Fixes failing instrumentation tests on Nakasi

content/browser/renderer_host/render_widget_host_view_android.cc

Index: content/browser/renderer_host/render_widget_host_view_android.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_android.cc b/content/browser/renderer_host/render_widget_host_view_android.cc
index a7586d02309356c1eaf2ff01b681258a8eccc742..2f6da47fedeb5c59f455bbcac2154d890ae4d20a 100644
--- a/content/browser/renderer_host/render_widget_host_view_android.cc
+++ b/content/browser/renderer_host/render_widget_host_view_android.cc
@@ -553,7 +553,8 @@ void RenderWidgetHostViewAndroid::LockCompositingSurface() {
 }
 
 void RenderWidgetHostViewAndroid::UnlockCompositingSurface() {
-  if (!frame_evictor_->HasFrame() || locks_on_frame_count_ == 0)
+  if (!frame_evictor_->HasFrame() || locks_on_frame_count_ == 0 ||
+      !layer_.get())

[no sievers, 2016/03/18 00:42:15]

I'm worried that this can mess up our |locks_on_frame_count_| and we end up
creating a new |layer_| and the lock count is now nonzero. It's also weird that
there is an early-out here for 'locks_on_frame_count_ == 0' which explicitly
seems to allow unbalanced calls.

Is the problem maybe this sequence?
void RenderWidgetHostViewAndroid::Destroy() {
  RemoveLayers();
  SetContentViewCore(NULL); -> can call ReleaseLocksOnSurface()

Note that there is another call to RemoveLayers() at the top of
SetContentViewCore().

It think it makes sense to ensure that we release locks on the 'compositing
surface' (which really is the layer) before we delete the layer.

[Jinsuk Kim, 2016/03/21 04:52:35]

locks_on_frame_count_ == 0 can be removed and replaced with DCHECK_EQ as done in
ReleaseLocksOnSurface(). For that, called frame_evictor_->DiscardedFrame()
before DestroyDelegatedContent() (please see  EvictDelegatedFrame()) to have
frame_evictor_->HasFrame() return false.

     return;
 
   DCHECK(HasValidFrame());
@@ -806,6 +807,7 @@ void RenderWidgetHostViewAndroid::RenderProcessGone(
 }
 
 void RenderWidgetHostViewAndroid::Destroy() {
+  host_->ViewDestroyed();
   RemoveLayers();
   SetContentViewCore(NULL);