Reducing CPU cycles of hidden/minimized browser windows

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/file_util.h"
 #include "base/metrics/histogram.h"
@@ skipping 703 matching lines @@
 // WebContentsViewAura, private:
 
 WebContentsViewAura::~WebContentsViewAura() {
   if (!window_)
     return;
 
   window_observer_.reset();
 
   // Window needs a valid delegate during its destructor, so we explicitly
   // delete it here.
+  window_->RemoveObserver(this);
   window_.reset();
 }
 
 void WebContentsViewAura::SetupOverlayWindowForTesting() {
   if (navigation_overlay_)
     navigation_overlay_->SetupForTesting();
 }
 
 void WebContentsViewAura::SetTouchEditableForTest(
     TouchEditableImplAura* touch_editable) {
@@ skipping 304 matching lines @@
   // NOTE: we ignore |initial_size| since in some cases it's wrong (such as
   // if the bookmark bar is not shown and you create a new tab). The right
   // value is set shortly after this, so its safe to ignore.
 
   aura::Env::CreateInstance(true);
   window_.reset(new aura::Window(this));
   window_->set_owned_by_parent(false);
   window_->SetType(ui::wm::WINDOW_TYPE_CONTROL);
   window_->SetTransparent(false);
   window_->Init(aura::WINDOW_LAYER_NOT_DRAWN);
+  window_->AddObserver(this);
   aura::Window* root_window = context ? context->GetRootWindow() : NULL;
   if (root_window) {
     // There are places where there is no context currently because object
     // hierarchies are built before they're attached to a Widget. (See
     // views::WebView as an example; GetWidget() returns NULL at the point
     // where we are created.)
     //
     // It should be OK to not set a default parent since such users will
     // explicitly add this WebContentsViewAura to their tree after they create
     // us.
@@ skipping 363 matching lines @@
   // then destroying it in the WebContentsViewAura destructor can trigger other
   // virtual functions to be called (e.g. OnImplicitAnimationsCompleted()). So
   // destroy the overscroll window here.
   navigation_overlay_.reset();
   overscroll_window_.reset();
 }
 
 void WebContentsViewAura::OnWindowDestroyed(aura::Window* window) {
 }
 
 void WebContentsViewAura::OnWindowTargetVisibilityChanged(bool visible) {

[sky, 2014/05/16 20:14:58]

I don't think you want this anymore.

   if (visible)
     web_contents_->WasShown();
   else
     web_contents_->WasHidden();
 }
 
 bool WebContentsViewAura::HasHitTestMask() const {
   return false;
 }
 
@@ skipping 106 matching lines @@
   web_contents_->GetRenderViewHost()->DragTargetDrop(
       event.location(),
       gfx::Screen::GetScreenFor(GetNativeView())->GetCursorScreenPoint(),
       ConvertAuraEventFlagsToWebInputEventModifiers(event.flags()));
   if (drag_dest_delegate_)
     drag_dest_delegate_->OnDrop();
   current_drop_data_.reset();
   return ConvertFromWeb(current_drag_op_);
 }
 
+void WebContentsViewAura::OnWindowParentChanged(aura::Window* window,
+                                                aura::Window* parent) {
+  if (!parent || parent->IsVisible())

[sky, 2014/05/16 20:14:58]

I don't get why you're tracking visibility of the parent to determine whether
this is visible here (and below). I see your comment, but that doesn't explain.
What flash? What is causing the flast?

I also suspect your changes may invoke WasShow (or WasHidden) multiple times in
a row. I don't know that the rest of the code deals well with that.

Lastly, how a test?

+    web_contents_->WasShown();
+  else
+    web_contents_->WasHidden();
+}
+
+void WebContentsViewAura::OnWindowVisibilityChanged(aura::Window* window,
+                                                    bool visible) {
+  aura::Window* parent = window_->parent();
+  if (!parent)
+    return;
+
+  // Follow the visibility of the parent window since e.g. navigation
+  // operations could otherwise cause a flash.
+  if (parent->IsVisible())
+    web_contents_->WasShown();
+  else
+    web_contents_->WasHidden();
+}
+
 }  // namespace content