Revert of Snap RWHVA and resize the legacy window on Windows whenever the ancestor window's bounds change.

content/browser/web_contents/web_contents_view_aura.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/web_contents/web_contents_view_aura.h"
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/files/file_util.h"
 #include "base/metrics/histogram.h"
@@ skipping 486 matching lines @@
     aura::Window* root_window = view_->window_->GetRootWindow();
     if (root_window) {
       root_window->RemoveObserver(this);
       const aura::Window::Windows& root_children = root_window->children();
       for (size_t i = 0; i < root_children.size(); ++i)
         root_children[i]->RemoveObserver(this);
     }
 #endif
   }
 
+  // Overridden from aura::WindowObserver:
+  void OnWindowHierarchyChanged(
+      const aura::WindowObserver::HierarchyChangeParams& params) override {
+    if (params.receiver != view_->window_.get() ||
+        !params.target->Contains(view_->window_.get())) {
+      return;
+    }
+
+    // Use the new parent's root window for calculating HiDPI subpixel offset.
+    RenderWidgetHostViewAura* rwhv = ToRenderWidgetHostViewAura(
+        view_->web_contents_->GetRenderWidgetHostView());
+    if (rwhv)
+      rwhv->SnapToPhysicalPixelBoundary();
+  }
+
 #if defined(OS_WIN)
   // Constrained windows are added as children of the parent's parent's view
   // which may overlap with windowed NPAPI plugins. In that case, tell the RWHV
   // so that it can update the plugins' cutout rects accordingly.
   // Note: this is hard coding how Chrome layer adds its dialogs. Since NPAPI is
   // going to be deprecated in a year, this is ok for now. The test for this is
   // PrintPreviewTest.WindowedNPAPIPluginHidden.
   virtual void OnWindowAdded(aura::Window* new_window) override {
     if (!new_window->Contains(view_->window_.get())) {
       // Skip the case when the parent moves to the root window.
@@ skipping 1114 matching lines @@
   if (visible) {
     if (!web_contents_->should_normally_be_visible())
       web_contents_->WasShown();
   } else {
     if (web_contents_->should_normally_be_visible())
       web_contents_->WasHidden();
   }
 }
 
 }  // namespace content