Resume RT-animations after a pauseSurface

Bug: 18203577

The issue occurs as a result of performTraversals() both doing
a window relayout call *and* early-returning because it's not dirty.

To fix this pauseSurface() returns whether or not the RT-side is
"dirty" to force ViewRootImpl to do a draw even if mDirty is
otherwise empty.

Change-Id: I534f367e75d18d273ebf14df3927f5c464ef6bef
diff --git a/libs/hwui/renderthread/RenderThread.cpp b/libs/hwui/renderthread/RenderThread.cpp
index f887103..38cb4cd 100644
--- a/libs/hwui/renderthread/RenderThread.cpp
+++ b/libs/hwui/renderthread/RenderThread.cpp
@@ -314,9 +314,11 @@
     mPendingRegistrationFrameCallbacks.insert(callback);
 }
 
-void RenderThread::removeFrameCallback(IFrameCallback* callback) {
-    mFrameCallbacks.erase(callback);
-    mPendingRegistrationFrameCallbacks.erase(callback);
+bool RenderThread::removeFrameCallback(IFrameCallback* callback) {
+    size_t erased;
+    erased = mFrameCallbacks.erase(callback);
+    erased |= mPendingRegistrationFrameCallbacks.erase(callback);
+    return erased;
 }
 
 void RenderThread::pushBackFrameCallback(IFrameCallback* callback) {