aw: Reset parent draw constraints on tear down

Without this, the same webview getting attached again but at a different
part of the view tree would be getting stale and completely wrong parent
draw constraints.

A classic example of this is when webview going into full screen video
mode.

BUG=

Review URL: https://codereview.chromium.org/486833002

Cr-Commit-Position: refs/heads/master@{#290450}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@290450 0039d316-1c4b-4281-b951-d872f2087c98

android_webview/browser/hardware_renderer.cc

@@ -118,6 +118,10 @@ HardwareRenderer::~HardwareRenderer() {
 #endif  // DCHECK_IS_ON
 
   resource_collection_->SetClient(NULL);
+
+  // Reset draw constraints.
+  shared_renderer_state_->UpdateDrawConstraints(
+      ParentCompositorDrawConstraints());
 }
 
 void HardwareRenderer::DidBeginMainFrame() {

android_webview/browser/shared_renderer_state.cc

@@ -146,12 +146,15 @@ scoped_ptr<DrawGLInput> SharedRendererState::PassDrawGLInput() {
   return draw_gl_input_.Pass();
 }
 
+void SharedRendererState::UpdateDrawConstraints(
+    const ParentCompositorDrawConstraints& parent_draw_constraints) {
+  base::AutoLock lock(lock_);
+  parent_draw_constraints_ = parent_draw_constraints;
+}
+
 void SharedRendererState::PostExternalDrawConstraintsToChildCompositor(
     const ParentCompositorDrawConstraints& parent_draw_constraints) {
-  {
-    base::AutoLock lock(lock_);
-    parent_draw_constraints_ = parent_draw_constraints;
-  }
+  UpdateDrawConstraints(parent_draw_constraints);
 
   // No need to hold the lock_ during the post task.
   ui_loop_->PostTask(

android_webview/browser/shared_renderer_state.h

@@ -57,6 +57,8 @@ class SharedRendererState {
   scoped_ptr<DrawGLInput> PassDrawGLInput();
 
   bool IsInsideHardwareRelease() const;
+  void UpdateDrawConstraints(
+      const ParentCompositorDrawConstraints& parent_draw_constraints);
   void PostExternalDrawConstraintsToChildCompositor(
       const ParentCompositorDrawConstraints& parent_draw_constraints);