Add observers for DIP scale change.

content/browser/android/content_view_core_impl.h

Index: content/browser/android/content_view_core_impl.h
diff --git a/content/browser/android/content_view_core_impl.h b/content/browser/android/content_view_core_impl.h
index 7ec22345bd8056a5bae7522fdcb2b54142dfaf06..0de3d43ec4a357c6d010478dfdf6f18fb67e6c1d 100644
--- a/content/browser/android/content_view_core_impl.h
+++ b/content/browser/android/content_view_core_impl.h
@@ -50,6 +50,7 @@ class ContentViewCoreImpl : public ContentViewCore,
       JNIEnv* env,
       const base::android::JavaRef<jobject>& obj,
       WebContents* web_contents,
+      float dpi_scale,
       const base::android::JavaRef<jobject>& java_bridge_retained_object_set);
 
   // ContentViewCore implementation.
@@ -217,6 +218,10 @@ class ContentViewCoreImpl : public ContentViewCore,
                 const base::android::JavaParamRef<jobject>& obj,
                 jboolean focused);
 
+  void SetDIPScale(JNIEnv* env,
+                   const base::android::JavaParamRef<jobject>& obj,
+                   jfloat dipScale);
+
   jint GetBackgroundColor(JNIEnv* env, jobject obj);
   void SetAllowJavascriptInterfacesInspection(
       JNIEnv* env,
@@ -407,6 +412,7 @@ class ContentViewCoreImpl : public ContentViewCore,
   // --------------------------------------------------------------------------
 
   void InitWebContents();
+  void SendScreenRectsAndResizeWidget();
 
   RenderWidgetHostViewAndroid* GetRenderWidgetHostViewAndroid() const;
 
@@ -443,7 +449,7 @@ class ContentViewCoreImpl : public ContentViewCore,
   float page_scale_;
 
   // Device scale factor.
-  const float dpi_scale_;
+  float dpi_scale_;
 
   // Observer to notify of lifecyle changes.
   base::ObserverList<ContentViewCoreImplObserver> observer_list_;