Highlighting sectioned apps on fast-scroll.

- This CL fixes an old assumption we had about the height
  of rows in AllApps, and ensures that we account for the
  difference in height between the predictive icons and the
  normal icons.
- In addition, we refactor FastBitmapDrawable to have multiple
  states, which it manages in drawing itself, including the
  press state and fast scroll focus states.  And we also refactor
  some of the fast scroll logic in the all apps recycler view
  out to its own class.

Change-Id: I1988159b2767df733bbbfc7dc601859cde6c9943

src/com/android/launcher3/allapps/AllAppsGridAdapter.java

@@ -69,6 +69,10 @@ public class AllAppsGridAdapter extends RecyclerView.Adapter<AllAppsGridAdapter.
     // The message to continue to a market search when there are no filtered results
     public static final int SEARCH_MARKET_VIEW_TYPE = 5;
 
+    public interface BindViewCallback {
+        public void onBindView(ViewHolder holder);
+    }
+
     /**
      * ViewHolder for each icon.
      */
@@ -328,6 +332,7 @@ public class AllAppsGridAdapter extends RecyclerView.Adapter<AllAppsGridAdapter.
     private View.OnTouchListener mTouchListener;
     private View.OnClickListener mIconClickListener;
     private View.OnLongClickListener mIconLongClickListener;
+    private BindViewCallback mBindViewCallback;
     @Thunk final Rect mBackgroundPadding = new Rect();
     @Thunk int mPredictionBarDividerOffset;
     @Thunk int mAppsPerRow;
@@ -424,6 +429,13 @@ public class AllAppsGridAdapter extends RecyclerView.Adapter<AllAppsGridAdapter.
         }
     }
 
+    /**
+     * Sets the callback for when views are bound.
+     */
+    public void setBindViewCallback(BindViewCallback cb) {
+        mBindViewCallback = cb;
+    }
+
     /**
      * Notifies the adapter of the background padding so that it can draw things correctly in the
      * item decorator.
@@ -529,6 +541,15 @@ public class AllAppsGridAdapter extends RecyclerView.Adapter<AllAppsGridAdapter.
                 }
                 break;
         }
+        if (mBindViewCallback != null) {
+            mBindViewCallback.onBindView(holder);
+        }
+    }
+
+    @Override
+    public boolean onFailedToRecycleView(ViewHolder holder) {
+        // Always recycle and we will reset the view when it is bound
+        return true;
     }
 
     @Override