Add observers for DIP scale change.

content/browser/android/content_view_core_impl.cc

Index: content/browser/android/content_view_core_impl.cc
diff --git a/content/browser/android/content_view_core_impl.cc b/content/browser/android/content_view_core_impl.cc
index 7854c3e44ecb2dd4432142a395239ddef0b483d0..9913e63635e07cf48fe0b3205b1212f4c63900af 100644
--- a/content/browser/android/content_view_core_impl.cc
+++ b/content/browser/android/content_view_core_impl.cc
@@ -209,13 +209,14 @@ ContentViewCoreImpl::ContentViewCoreImpl(
     WebContents* web_contents,
     const JavaRef<jobject>& view_android_delegate,
     ui::WindowAndroid* window_android,
+    float dpi_scale,
     const JavaRef<jobject>& java_bridge_retained_object_set)
     : WebContentsObserver(web_contents),
       java_ref_(env, obj),
       view_(view_android_delegate),
       web_contents_(static_cast<WebContentsImpl*>(web_contents)),
       page_scale_(1),
-      dpi_scale_(ui::GetScaleFactorForNativeView(&view_)),
+      dpi_scale_(dpi_scale),
       device_orientation_(0),
       accessibility_enabled_(false) {
   CHECK(web_contents) <<
@@ -803,6 +804,15 @@ float ContentViewCoreImpl::GetBottomControlsHeightDip() const {
   return GetBottomControlsHeightPix() / dpi_scale();
 }
 
+void ContentViewCoreImpl::SendScreenRectsAndResizeWidget() {
+  RenderWidgetHostViewAndroid* view = GetRenderWidgetHostViewAndroid();
+  if (view) {
+    // |SendScreenRects()| indirectly calls GetViewSize() that asks Java layer.
+    web_contents_->SendScreenRects();
+    view->WasResized();
+  }
+}
+
 void ContentViewCoreImpl::MoveRangeSelectionExtent(const gfx::PointF& extent) {
   if (!web_contents_)
     return;
@@ -868,6 +878,16 @@ void ContentViewCoreImpl::SetFocus(JNIEnv* env,
   SetFocusInternal(focused);
 }
 
+void ContentViewCoreImpl::SetDIPScale(JNIEnv* env,
+                                      const JavaParamRef<jobject>& obj,
+                                      jfloat dpi_scale) {
+  if (dpi_scale_ == dpi_scale)
+    return;
+
+  dpi_scale_ = dpi_scale;
+  SendScreenRectsAndResizeWidget();
+}
+
 void ContentViewCoreImpl::SetFocusInternal(bool focused) {
   if (!GetRenderWidgetHostViewAndroid())
     return;
@@ -1236,16 +1256,12 @@ void ContentViewCoreImpl::RemoveJavascriptInterface(
 
 void ContentViewCoreImpl::WasResized(JNIEnv* env,
                                      const JavaParamRef<jobject>& obj) {
-  RenderWidgetHostViewAndroid* view = GetRenderWidgetHostViewAndroid();
   gfx::Size physical_size(
       Java_ContentViewCore_getPhysicalBackingWidthPix(env, obj),
       Java_ContentViewCore_getPhysicalBackingHeightPix(env, obj));
   view_.GetLayer()->SetBounds(physical_size);
 
-  if (view) {
-    web_contents_->SendScreenRects();
-    view->WasResized();
-  }
+  SendScreenRectsAndResizeWidget();
 }
 
 long ContentViewCoreImpl::GetNativeImeAdapter(
@@ -1555,11 +1571,12 @@ jlong Init(JNIEnv* env,
            const JavaParamRef<jobject>& web_contents,
            const JavaParamRef<jobject>& view_android_delegate,
            jlong window_android,
+           jfloat dipScale,
            const JavaParamRef<jobject>& retained_objects_set) {
   ContentViewCoreImpl* view = new ContentViewCoreImpl(
       env, obj, WebContents::FromJavaWebContents(web_contents),
       view_android_delegate,
-      reinterpret_cast<ui::WindowAndroid*>(window_android),
+      reinterpret_cast<ui::WindowAndroid*>(window_android), dipScale,
       retained_objects_set);
   return reinterpret_cast<intptr_t>(view);
 }