Fix and enforce the last two remaining error-prone warnings.

Test: ./gradlew assebleErrorProne
Change-Id: I2d6c11e57b4013b3b550233480af653efe7ee3ae
diff --git a/buildSrc/src/main/groovy/android/support/SupportLibraryPlugin.groovy b/buildSrc/src/main/groovy/android/support/SupportLibraryPlugin.groovy
index 8f3966b..459210e 100644
--- a/buildSrc/src/main/groovy/android/support/SupportLibraryPlugin.groovy
+++ b/buildSrc/src/main/groovy/android/support/SupportLibraryPlugin.groovy
@@ -189,7 +189,9 @@
 
                             // Enforce the following checks.
                             '-Xep:MissingOverride:ERROR',
+                            '-Xep:NarrowingCompoundAssignment:ERROR',
                             '-Xep:ClassNewInstance:ERROR',
+                            '-Xep:ClassCanBeStatic:ERROR',
                             '-Xep:SynchronizeOnNonFinalField:ERROR'
                     ]
                 }
diff --git a/core-ui/java/android/support/v4/widget/CircularProgressDrawable.java b/core-ui/java/android/support/v4/widget/CircularProgressDrawable.java
index 34b1874..d4fdc5a 100644
--- a/core-ui/java/android/support/v4/widget/CircularProgressDrawable.java
+++ b/core-ui/java/android/support/v4/widget/CircularProgressDrawable.java
@@ -610,7 +610,7 @@
      * A private class to do all the drawing of CircularProgressDrawable, which includes background,
      * progress spinner and the arrow. This class is to separate drawing from animation.
      */
-    private class Ring {
+    private static class Ring {
         final RectF mTempBounds = new RectF();
         final Paint mPaint = new Paint();
         final Paint mArrowPaint = new Paint();
diff --git a/transition/api14/android/support/transition/GhostViewApi14.java b/transition/api14/android/support/transition/GhostViewApi14.java
index c918651..38acef2 100644
--- a/transition/api14/android/support/transition/GhostViewApi14.java
+++ b/transition/api14/android/support/transition/GhostViewApi14.java
@@ -150,8 +150,8 @@
         final int[] viewLocation = new int[2];
         getLocationOnScreen(location);
         mView.getLocationOnScreen(viewLocation);
-        viewLocation[0] -= mView.getTranslationX();
-        viewLocation[1] -= mView.getTranslationY();
+        viewLocation[0] = (int) (viewLocation[0] - mView.getTranslationX());
+        viewLocation[1] = (int) (viewLocation[1] - mView.getTranslationY());
         mDeltaX = viewLocation[0] - location[0];
         mDeltaY = viewLocation[1] - location[1];
         // Monitor invalidation of the target view.