Make code path for bounds changes getting to renderer less brittle

content/browser/web_contents/aura/native_view_screen_bounds_observer.cc

Index: content/browser/web_contents/aura/native_view_screen_bounds_observer.cc
diff --git a/content/browser/web_contents/aura/native_view_screen_bounds_observer.cc b/content/browser/web_contents/aura/native_view_screen_bounds_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..5334232c3643e01f29dd4b09af4ab3bd32286a07
--- /dev/null
+++ b/content/browser/web_contents/aura/native_view_screen_bounds_observer.cc
@@ -0,0 +1,134 @@
+// Copyright (c) 2013 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/aura/native_view_screen_bounds_observer.h"
+
+#include <algorithm>
+
+#include "base/debug/trace_event.h"
+#include "content/browser/web_contents/web_contents_view_aura.h"
+#include "ui/aura/test/aura_test_base.h"
+#include "ui/aura/window.h"
+
+namespace content {
+
+NativeViewScreenBoundsObserver::NativeViewScreenBoundsObserver(
+    NativeViewScreenBoundsObserverDelegate* delegate,
+    aura::Window* window)
+    : delegate_(delegate),
+      window_(window) {
+  DCHECK(delegate);
+  DCHECK(window);
+  delegate_ = delegate;
+  window_ = window;
+  std::set<aura::Window*> windows_to_root = CollectAllWindowsToRoot(window_);
+  AddToObserved(windows_to_root);
+}
+
+NativeViewScreenBoundsObserver::~NativeViewScreenBoundsObserver() {
+  RemoveFromObserved(observed_);
+  if (window_->GetDispatcher())
+    window_->GetDispatcher()->RemoveRootWindowObserver(this);
+}
+
+void NativeViewScreenBoundsObserver::OnWindowParentChanged(
+    aura::Window* window,
+    aura::Window* parent) {
+  std::set<aura::Window*> windows_to_root = CollectAllWindowsToRoot(window_);
+  std::set<aura::Window*> difference;
+  std::set_difference(
+      observed_.begin(),
+      observed_.end(),
+      windows_to_root.begin(),
+      windows_to_root.end(),
+      std::inserter(difference, difference.end()));
+  RemoveFromObserved(difference);
+
+  difference.clear();
+  std::set_difference(
+      windows_to_root.begin(),
+      windows_to_root.end(),
+      observed_.begin(),
+      observed_.end(),
+      std::inserter(difference, difference.end()));
+  AddToObserved(difference);
+}
+
+void NativeViewScreenBoundsObserver::OnWindowBoundsChanged(
+    aura::Window* window,
+    const gfx::Rect& old_bounds,
+    const gfx::Rect& new_bounds) {
+  if (old_bounds.size() == new_bounds.size()) {
+    delegate_->OnScreenPositionChanged();
+  } else {
+    delegate_->OnScreenBoundsChanged();
+  }
+}
+
+void NativeViewScreenBoundsObserver::OnWindowAddedToRootWindow(
+    aura::Window* window) {
+  if (window == window_ && window_->GetDispatcher())
+    window_->GetDispatcher()->AddRootWindowObserver(this);
+}
+
+void NativeViewScreenBoundsObserver::OnWindowRemovingFromRootWindow(
+    aura::Window* window) {
+  if (window == window_ && window_->GetDispatcher())
+    window_->GetDispatcher()->RemoveRootWindowObserver(this);
+}
+
+void NativeViewScreenBoundsObserver::OnRootWindowHostMoved(
+    const aura::RootWindow* root,
+    const gfx::Point& new_origin) {
+  TRACE_EVENT1("ui",
+               "WebContentsViewAura::WindowObserver::OnWindowTreeHostMoved",
+               "new_origin", new_origin.ToString());
+
+  // This is for the desktop case (i.e. Aura desktop).
+  delegate_->OnScreenPositionChanged();
+}
+
+std::set<aura::Window*> NativeViewScreenBoundsObserver::CollectAllWindowsToRoot(
+    aura::Window* window) {
+  std::set<aura::Window*> ret_val;
+  if (window)
+    ret_val.insert(window);
+  while (window && window->parent()) {
+    ret_val.insert(window->parent());
+    window = window->parent();
+  }
+  return ret_val;
+}
+
+void NativeViewScreenBoundsObserver::AddToObserved(
+    const std::set<aura::Window*>& windows) {
+  for (std::set<aura::Window*>::iterator iter = windows.begin();
+       iter != windows.end();
+       ++iter) {
+    if (observed_.end() == observed_.find(*iter)) {
+      (*iter)->AddObserver(this);
+      observed_.insert(*iter);
+    }
+  }
+}
+
+void NativeViewScreenBoundsObserver::RemoveFromObserved(
+    const std::set<aura::Window*>& windows) {
+  // Since windows can possibly be |observer_| we cannot blindly iterate and
+  // delete, since const & means that |windows| is a reference to
+  // |observer_|. Thus if we erase an entry from |observed_| it may be erased
+  // from |windows| which we are iterating.
+  for (std::set<aura::Window*>::iterator iter = windows.begin();
+       iter != windows.end();) {
+    std::set<aura::Window*>::iterator next = iter;
+    next++;
+    if (observed_.end() != observed_.find(*iter)) {
+      (*iter)->RemoveObserver(this);
+      observed_.erase(*iter);
+    }
+    iter = next;
+  }
+}
+
+}  // namespace content