Use contents size for android_webview layout.

android_webview/browser/renderer_host/aw_render_view_host_ext.h

Index: android_webview/browser/renderer_host/aw_render_view_host_ext.h
diff --git a/android_webview/browser/renderer_host/aw_render_view_host_ext.h b/android_webview/browser/renderer_host/aw_render_view_host_ext.h
index 3007f15556effb5195a1534f2e49d577d52ff25b..f255c8c2dad8bbc00eaaa649775fde78a54e1c5f 100644
--- a/android_webview/browser/renderer_host/aw_render_view_host_ext.h
+++ b/android_webview/browser/renderer_host/aw_render_view_host_ext.h
@@ -11,6 +11,7 @@
 #include "base/callback_forward.h"
 #include "base/threading/non_thread_safe.h"
 #include "third_party/skia/include/core/SkColor.h"
+#include "ui/gfx/size.h"
 
 class GURL;
 
@@ -25,6 +26,8 @@ class AwRenderViewHostExtClient {
  public:
   // Called when the RenderView page scale changes.
   virtual void OnWebLayoutPageScaleFactorChanged(float page_scale_factor) = 0;
+  virtual void OnWebLayoutContentsSizeChanged(
+      const gfx::Size& contents_size) = 0;
 
  protected:
   virtual ~AwRenderViewHostExtClient() {}
@@ -86,6 +89,7 @@ class AwRenderViewHostExt : public content::WebContentsObserver,
   void OnDocumentHasImagesResponse(int msg_id, bool has_images);
   void OnUpdateHitTestData(const AwHitTestData& hit_test_data);
   void OnPageScaleFactorChanged(float page_scale_factor);
+  void OnContentsSizeChanged(const gfx::Size& contents_size);
 
   bool IsRenderViewReady() const;