Make WebView respond to device 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 df0276b8d4ecdc7b0c6f7deb023d748e14db056a..7dcb00dd9a607fc5a28e25f05dc1f1f01be71649 100644
--- a/content/browser/android/content_view_core_impl.h
+++ b/content/browser/android/content_view_core_impl.h
@@ -231,6 +231,9 @@ class ContentViewCoreImpl : public ContentViewCore,
   void SetFocus(JNIEnv* env,
                 const base::android::JavaParamRef<jobject>& obj,
                 jboolean focused);
+  void SetDeviceScaleFactor(JNIEnv* env,
+                            const base::android::JavaParamRef<jobject>& obj,
+                            jfloat device_scale);
 
   jint GetBackgroundColor(JNIEnv* env, jobject obj);
   void SetAllowJavascriptInterfacesInspection(
@@ -459,7 +462,7 @@ 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_;