[video_player] Add URL for exoplayer to maven for all dependents (#3979)

JCenter has the older version of ExoPlayer that the plugin currently uses, but Google's maven server doesn't so we need to add a workaround in the short term for the removal of JCenter in #3924 to avoid breaking clients of video_player.

This was not caught in presubmit because the video_player example had this same workaround left over from an issue several years ago that caused JCenter not to have that version either; that issue was since fixed, but the workaround was never removed. This removes the example-level workaround so the example won't mask exoplayer maven issues in the future.

(Also temporarily re-adds the workaround to the camera example, which broke post-publishing, to fix the tree. All example workarounds should be removable once this change is published.)
diff --git a/packages/camera/camera/example/android/build.gradle b/packages/camera/camera/example/android/build.gradle
index 456d020..74d95cf 100644
--- a/packages/camera/camera/example/android/build.gradle
+++ b/packages/camera/camera/example/android/build.gradle
@@ -13,6 +13,9 @@
     repositories {
         google()
         mavenCentral()
+        maven {
+            url 'https://google.bintray.com/exoplayer/'
+        }
     }
 }
 
diff --git a/packages/video_player/video_player/CHANGELOG.md b/packages/video_player/video_player/CHANGELOG.md
index c40faab..c3cddab 100644
--- a/packages/video_player/video_player/CHANGELOG.md
+++ b/packages/video_player/video_player/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 2.1.4
+
+* Add an exoplayer URL to the maven repositories to address
+  a possible build regression in 2.1.2.
+
 ## 2.1.3
 
 * Fix pointer value to boolean conversion analyzer warnings.
diff --git a/packages/video_player/video_player/android/build.gradle b/packages/video_player/video_player/android/build.gradle
index b87ed8e..2f0f5c1 100644
--- a/packages/video_player/video_player/android/build.gradle
+++ b/packages/video_player/video_player/android/build.gradle
@@ -17,6 +17,12 @@
     repositories {
         google()
         mavenCentral()
+        // Gradle versions older than 2.13.3 aren't published to the servers
+        // above, so add this URL as a workaround until upgrading past that
+        // version.
+        maven {
+            url 'https://google.bintray.com/exoplayer/'
+        }
     }
 }
 
diff --git a/packages/video_player/video_player/example/android/build.gradle b/packages/video_player/video_player/example/android/build.gradle
index 74d95cf..456d020 100644
--- a/packages/video_player/video_player/example/android/build.gradle
+++ b/packages/video_player/video_player/example/android/build.gradle
@@ -13,9 +13,6 @@
     repositories {
         google()
         mavenCentral()
-        maven {
-            url 'https://google.bintray.com/exoplayer/'
-        }
     }
 }
 
diff --git a/packages/video_player/video_player/pubspec.yaml b/packages/video_player/video_player/pubspec.yaml
index a63803d..0587dd4 100644
--- a/packages/video_player/video_player/pubspec.yaml
+++ b/packages/video_player/video_player/pubspec.yaml
@@ -3,7 +3,7 @@
   widgets on Android, iOS, and web.
 repository: https://github.com/flutter/plugins/tree/master/packages/video_player/video_player
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+video_player%22
-version: 2.1.3
+version: 2.1.4
 
 environment:
   sdk: ">=2.12.0 <3.0.0"