Fixed Android animation framework, for using interpolators that do not start at 0.0f

There is a bug that affects interpolators that do not return 0.0f when given 0.0f as input. All default interpolators in Android do return 0.0f, which is why it hasn't been
noticed. Some custom interpolators can for example run backwards, returning 1.0f when given input 0.0f.

Author: Andreas Agvard

core/java/android/view/animation/Animation.java

@@ -880,7 +880,7 @@ public void initializeInvalidateRegion(int left, int top, int right, int bottom)
         region.inset(-1.0f, -1.0f);
         if (mFillBefore) {
             final Transformation previousTransformation = mPreviousTransformation;
-            applyTransformation(0.0f, previousTransformation);
+            applyTransformation(mInterpolator.getInterpolation(0.0f), previousTransformation);
         }
     }
 

core/java/android/view/animation/AnimationSet.java

@@ -282,7 +282,9 @@ public void initializeInvalidateRegion(int left, int top, int right, int bottom)
                 final Animation a = animations.get(i);
 
                 temp.clear();
-                a.applyTransformation(0.0f, temp);
+                final Interpolator interpolator = a.mInterpolator;
+                a.applyTransformation(interpolator != null ? interpolator.getInterpolation(0.0f)
+                        : 0.0f, temp);
                 previousTransformation.compose(temp);
             }
         }