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/RenderProxy.cpp b/libs/hwui/renderthread/RenderProxy.cpp
index 5d55ea6..6d063a4 100644
--- a/libs/hwui/renderthread/RenderProxy.cpp
+++ b/libs/hwui/renderthread/RenderProxy.cpp
@@ -156,15 +156,14 @@
 }
 
 CREATE_BRIDGE2(pauseSurface, CanvasContext* context, ANativeWindow* window) {
-    args->context->pauseSurface(args->window);
-    return NULL;
+    return (void*) args->context->pauseSurface(args->window);
 }
 
-void RenderProxy::pauseSurface(const sp<ANativeWindow>& window) {
+bool RenderProxy::pauseSurface(const sp<ANativeWindow>& window) {
     SETUP_TASK(pauseSurface);
     args->context = mContext;
     args->window = window.get();
-    postAndWait(task);
+    return (bool) postAndWait(task);
 }
 
 CREATE_BRIDGE7(setup, CanvasContext* context, int width, int height,