Cherry-pick #28846 and #28743 into flutter-2.6-candidate.11 (#28937)

Ignoring the web framework test since the failure originates from a repo synchronization issue between engine and framework. The new failing tests were sync'ed in from head in the test and the tested code doesn't exist in the engine at the time of branch cut. 

* Fixes FlutterSemanticsScrollView to not implement accessibility container API (#28846)

* add branch to test

* Replace jcenter() for mavenCentral() (#28777)

* Set MinimumOSVersion to iOS 9 in Info.plist (#28783)

* Do not use jcenter(), switch to mavenCentral() (#28738)

Co-authored-by: chunhtai <47866232+chunhtai@users.noreply.github.com>
Co-authored-by: Emmanuel Garcia <egarciad@google.com>
Co-authored-by: Jenn Magder <magder@google.com>
Co-authored-by: Dan Field <dnfield@google.com>
diff --git a/.ci.yaml b/.ci.yaml
index a920ab8..fc281a1 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -10,6 +10,7 @@
   - dev
   - beta
   - stable
+  - flutter-2.6-candidate.11
 
 platform_properties:
   linux:
diff --git a/shell/platform/android/test_runner/build.gradle b/shell/platform/android/test_runner/build.gradle
index 704dc7c..1cd4436 100644
--- a/shell/platform/android/test_runner/build.gradle
+++ b/shell/platform/android/test_runner/build.gradle
@@ -1,7 +1,7 @@
 buildscript {
   repositories {
     google()
-    jcenter()
+    mavenCentral()
   }
   dependencies {
     classpath "com.android.tools.build:gradle:7.0.0"
@@ -10,7 +10,7 @@
 
 repositories {
   google()
-  jcenter()
+  mavenCentral()
 }
 
 apply plugin: "com.android.library"
diff --git a/shell/platform/darwin/ios/framework/Info.plist b/shell/platform/darwin/ios/framework/Info.plist
index 420e803..7264dec 100644
--- a/shell/platform/darwin/ios/framework/Info.plist
+++ b/shell/platform/darwin/ios/framework/Info.plist
@@ -21,7 +21,7 @@
   <key>CFBundleVersion</key>
   <string>1.0</string>
   <key>MinimumOSVersion</key>
-  <string>8.0</string>
+  <string>9.0</string>
   <key>FlutterEngine</key>
   <string>{0}</string>
   <key>ClangVersion</key>
diff --git a/shell/platform/darwin/ios/framework/Source/FlutterSemanticsScrollView.mm b/shell/platform/darwin/ios/framework/Source/FlutterSemanticsScrollView.mm
index ad5dd0d..2bdde79 100644
--- a/shell/platform/darwin/ios/framework/Source/FlutterSemanticsScrollView.mm
+++ b/shell/platform/darwin/ios/framework/Source/FlutterSemanticsScrollView.mm
@@ -106,33 +106,4 @@
   return [[_semanticsObject children] count];
 }
 
-- (id)accessibilityElementAtIndex:(NSInteger)index {
-  SemanticsObject* child = [_semanticsObject children][index];
-
-  // Swap the original `SemanticsObject` to a `PlatformViewSemanticsContainer`
-  if (child.node.IsPlatformViewNode()) {
-    child.platformViewSemanticsContainer.index = index;
-    return child.platformViewSemanticsContainer;
-  }
-
-  if ([child hasChildren])
-    return [child accessibilityContainer];
-  return [child nativeAccessibility];
-}
-
-- (NSInteger)indexOfAccessibilityElement:(id)element {
-  if ([element isKindOfClass:[FlutterPlatformViewSemanticsContainer class]]) {
-    return ((FlutterPlatformViewSemanticsContainer*)element).index;
-  }
-
-  NSArray<SemanticsObject*>* children = [_semanticsObject children];
-  for (size_t i = 0; i < [children count]; i++) {
-    SemanticsObject* child = children[i];
-    if ((![child hasChildren] && child == element) ||
-        ([child hasChildren] && [child accessibilityContainer] == element))
-      return i;
-  }
-  return NSNotFound;
-}
-
 @end
diff --git a/testing/android_background_image/android/build.gradle b/testing/android_background_image/android/build.gradle
index bfe1241..51b93f9 100644
--- a/testing/android_background_image/android/build.gradle
+++ b/testing/android_background_image/android/build.gradle
@@ -3,7 +3,7 @@
 buildscript {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
     dependencies {
         classpath 'com.android.tools.build:gradle:7.0.0'
@@ -16,7 +16,7 @@
 allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 }
 
diff --git a/testing/scenario_app/android/build.gradle b/testing/scenario_app/android/build.gradle
index 2308fb2..007f634 100644
--- a/testing/scenario_app/android/build.gradle
+++ b/testing/scenario_app/android/build.gradle
@@ -3,7 +3,7 @@
 buildscript {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
     dependencies {
         classpath 'com.android.tools.build:gradle:7.0.0'
@@ -23,7 +23,7 @@
 allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 }
 
diff --git a/tools/cipd/android_embedding_bundle/build.gradle b/tools/cipd/android_embedding_bundle/build.gradle
index e93098c..6c25575 100644
--- a/tools/cipd/android_embedding_bundle/build.gradle
+++ b/tools/cipd/android_embedding_bundle/build.gradle
@@ -12,7 +12,7 @@
 buildscript {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
     dependencies {
         classpath "com.android.tools.build:gradle:3.5.0"
@@ -22,7 +22,7 @@
 allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 }