Replace ANDROID_HOME user messages with ANDROID_SDK_ROOT (#59867)

diff --git a/dev/bots/test.dart b/dev/bots/test.dart
index 6670ef0..d9a9f6e 100644
--- a/dev/bots/test.dart
+++ b/dev/bots/test.dart
@@ -1113,7 +1113,7 @@
       ? Platform.environment['ANDROID_SDK_ROOT']
       : Platform.environment['ANDROID_HOME'];
   if (androidSdkRoot == null || androidSdkRoot.isEmpty) {
-    print('${red}Could not find Android SDK; set ANDROID_SDK_ROOT (or ANDROID_HOME).$reset');
+    print('${red}Could not find Android SDK; set ANDROID_SDK_ROOT.$reset');
     exit(1);
   }
   return <String, String>{
diff --git a/dev/devicelab/README.md b/dev/devicelab/README.md
index 4c6a062..609e844 100644
--- a/dev/devicelab/README.md
+++ b/dev/devicelab/README.md
@@ -94,7 +94,7 @@
 
 ## Prerequisites
 
-You must set the `ANDROID_HOME` or `ANDROID_SDK_ROOT` environment variable to run
+You must set `ANDROID_SDK_ROOT` environment variable to run
 tests on Android. If you have a local build of the Flutter engine, then you have
 a copy of the Android SDK at `.../engine/src/third_party/android_tools/sdk`.
 
diff --git a/dev/devicelab/lib/framework/adb.dart b/dev/devicelab/lib/framework/adb.dart
index 65163a0..959983c 100644
--- a/dev/devicelab/lib/framework/adb.dart
+++ b/dev/devicelab/lib/framework/adb.dart
@@ -690,8 +690,8 @@
 
   if (androidHome == null) {
     throw const DeviceException(
-      'The ANDROID_SDK_ROOT and ANDROID_HOME environment variables are '
-      'missing. At least one of these variables must point to the Android '
+      'The ANDROID_SDK_ROOT environment variable is '
+      'missing. The variable must point to the Android '
       'SDK directory containing platform-tools.'
     );
   }
diff --git a/dev/devicelab/lib/framework/apk_utils.dart b/dev/devicelab/lib/framework/apk_utils.dart
index 63415a6..fcba3cd 100644
--- a/dev/devicelab/lib/framework/apk_utils.dart
+++ b/dev/devicelab/lib/framework/apk_utils.dart
@@ -105,7 +105,7 @@
   final String androidHome = Platform.environment['ANDROID_HOME'] ??
       Platform.environment['ANDROID_SDK_ROOT'];
   if (androidHome == null || androidHome.isEmpty) {
-    throw Exception('Unset env flag: `ANDROID_HOME` or `ANDROID_SDK_ROOT`.');
+    throw Exception('Environment variable `ANDROID_SDK_ROOT` is not set.');
   }
   return androidHome;
 }
diff --git a/packages/flutter_tools/lib/src/android/android_device_discovery.dart b/packages/flutter_tools/lib/src/android/android_device_discovery.dart
index 634e1be..a5f5290 100644
--- a/packages/flutter_tools/lib/src/android/android_device_discovery.dart
+++ b/packages/flutter_tools/lib/src/android/android_device_discovery.dart
@@ -59,10 +59,10 @@
       )).stdout.trim();
     } on ArgumentError catch (exception) {
       throwToolExit('Unable to find "adb", check your Android SDK installation and '
-        'ANDROID_HOME environment variable: ${exception.message}');
+        '$kAndroidSdkRoot environment variable: ${exception.message}');
     } on ProcessException catch (exception) {
       throwToolExit('Unable to run "adb", check your Android SDK installation and '
-        'ANDROID_HOME environment variable: ${exception.executable}');
+        '$kAndroidSdkRoot environment variable: ${exception.executable}');
     }
     final List<AndroidDevice> devices = <AndroidDevice>[];
     parseADBDeviceOutput(
diff --git a/packages/flutter_tools/lib/src/android/android_sdk.dart b/packages/flutter_tools/lib/src/android/android_sdk.dart
index 9695442..1179eba 100644
--- a/packages/flutter_tools/lib/src/android/android_sdk.dart
+++ b/packages/flutter_tools/lib/src/android/android_sdk.dart
@@ -14,22 +14,24 @@
 import '../globals.dart' as globals;
 import 'android_studio.dart';
 
+// ANDROID_HOME is deprecated.
+// See https://developer.android.com/studio/command-line/variables.html#envar
 const String kAndroidHome = 'ANDROID_HOME';
 const String kAndroidSdkRoot = 'ANDROID_SDK_ROOT';
 
 // Android SDK layout:
 
-// $ANDROID_HOME/platform-tools/adb
+// $ANDROID_SDK_ROOT/platform-tools/adb
 
-// $ANDROID_HOME/build-tools/19.1.0/aapt, dx, zipalign
-// $ANDROID_HOME/build-tools/22.0.1/aapt
-// $ANDROID_HOME/build-tools/23.0.2/aapt
-// $ANDROID_HOME/build-tools/24.0.0-preview/aapt
-// $ANDROID_HOME/build-tools/25.0.2/apksigner
+// $ANDROID_SDK_ROOT/build-tools/19.1.0/aapt, dx, zipalign
+// $ANDROID_SDK_ROOT/build-tools/22.0.1/aapt
+// $ANDROID_SDK_ROOT/build-tools/23.0.2/aapt
+// $ANDROID_SDK_ROOT/build-tools/24.0.0-preview/aapt
+// $ANDROID_SDK_ROOT/build-tools/25.0.2/apksigner
 
-// $ANDROID_HOME/platforms/android-22/android.jar
-// $ANDROID_HOME/platforms/android-23/android.jar
-// $ANDROID_HOME/platforms/android-N/android.jar
+// $ANDROID_SDK_ROOT/platforms/android-22/android.jar
+// $ANDROID_SDK_ROOT/platforms/android-23/android.jar
+// $ANDROID_SDK_ROOT/platforms/android-N/android.jar
 
 final RegExp _numberedAndroidPlatformRe = RegExp(r'^android-([0-9]+)$');
 final RegExp _sdkVersionRe = RegExp(r'^ro.build.version.sdk=([0-9]+)$');
diff --git a/packages/flutter_tools/lib/src/android/gradle_utils.dart b/packages/flutter_tools/lib/src/android/gradle_utils.dart
index 7f741f8..9646949 100644
--- a/packages/flutter_tools/lib/src/android/gradle_utils.dart
+++ b/packages/flutter_tools/lib/src/android/gradle_utils.dart
@@ -304,6 +304,6 @@
   BuildEvent('unsupported-project', eventError: 'android-sdk-not-found', flutterUsage: globals.flutterUsage).send();
   throwToolExit(
     '$warningMark No Android SDK found. '
-    'Try setting the ANDROID_HOME environment variable.'
+    'Try setting the ANDROID_SDK_ROOT environment variable.'
   );
 }
diff --git a/packages/flutter_tools/test/commands.shard/permeable/build_aar_test.dart b/packages/flutter_tools/test/commands.shard/permeable/build_aar_test.dart
index 4c7e3bb..736c275 100644
--- a/packages/flutter_tools/test/commands.shard/permeable/build_aar_test.dart
+++ b/packages/flutter_tools/test/commands.shard/permeable/build_aar_test.dart
@@ -266,7 +266,7 @@
             arguments: <String>['--no-pub'],
           );
         }, throwsToolExit(
-          message: 'No Android SDK found. Try setting the ANDROID_HOME environment variable',
+          message: 'No Android SDK found. Try setting the ANDROID_SDK_ROOT environment variable',
         ));
       },
       overrides: <Type, Generator>{
diff --git a/packages/flutter_tools/test/commands.shard/permeable/build_apk_test.dart b/packages/flutter_tools/test/commands.shard/permeable/build_apk_test.dart
index 2d2c073..e449704 100644
--- a/packages/flutter_tools/test/commands.shard/permeable/build_apk_test.dart
+++ b/packages/flutter_tools/test/commands.shard/permeable/build_apk_test.dart
@@ -212,7 +212,7 @@
             arguments: <String>['--no-pub'],
           );
         }, throwsToolExit(
-          message: 'No Android SDK found. Try setting the ANDROID_HOME environment variable',
+          message: 'No Android SDK found. Try setting the ANDROID_SDK_ROOT environment variable',
         ));
       },
       overrides: <Type, Generator>{
diff --git a/packages/flutter_tools/test/commands.shard/permeable/build_appbundle_test.dart b/packages/flutter_tools/test/commands.shard/permeable/build_appbundle_test.dart
index a2a3700..2376dfb 100644
--- a/packages/flutter_tools/test/commands.shard/permeable/build_appbundle_test.dart
+++ b/packages/flutter_tools/test/commands.shard/permeable/build_appbundle_test.dart
@@ -197,7 +197,7 @@
             arguments: <String>['--no-pub'],
           );
         }, throwsToolExit(
-          message: 'No Android SDK found. Try setting the ANDROID_HOME environment variable',
+          message: 'No Android SDK found. Try setting the ANDROID_SDK_ROOT environment variable',
         ));
       },
       overrides: <Type, Generator>{
diff --git a/packages/flutter_tools/test/general.shard/android/gradle_test.dart b/packages/flutter_tools/test/general.shard/android/gradle_test.dart
index e7eeda1..54f655a 100644
--- a/packages/flutter_tools/test/general.shard/android/gradle_test.dart
+++ b/packages/flutter_tools/test/general.shard/android/gradle_test.dart
@@ -323,7 +323,7 @@
       expect(() {
         updateLocalProperties(project: FlutterProject.current());
       }, throwsToolExit(
-        message: '$warningMark No Android SDK found. Try setting the ANDROID_HOME environment variable.',
+        message: '$warningMark No Android SDK found. Try setting the ANDROID_SDK_ROOT environment variable.',
       ));
     }, overrides: <Type, Generator>{
       AndroidSdk: () => null,