Mac: Fix flickering while entering/leaving fullscreen low power video

chrome/browser/ui/cocoa/fullscreen_low_power_coordinator.h

 // Copyright 2016 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.
 
 #ifndef CHROME_BROWSER_UI_COCOA_FULLSCREEN_LOW_POWER_COORDINATOR_H_
 #define CHROME_BROWSER_UI_COCOA_FULLSCREEN_LOW_POWER_COORDINATOR_H_
 
 #include "ui/accelerated_widget_mac/accelerated_widget_mac.h"
 #include "ui/accelerated_widget_mac/fullscreen_low_power_coordinator.h"
 
@@ skipping 24 matching lines @@
                            const NSRect& infobar_frame,
                            const NSRect& content_frame,
                            const NSRect& download_shelf_frame);
   void SetHasActiveSheet(bool has_sheet);
   void ChildWindowsChanged();
 
   // ui::FullscreenLowPowerCoordinator implementation.
   void SetLowPowerLayerValid(bool valid) override;
   void WillLoseAcceleratedWidget() override;
 
+  // Call EnterOrExitLowPowerModeIfNeeded to wind down counters.
+  void TickEnterOrExitForTesting();
+
  private:
   // Determine if we should be fullscreen low power mode, and enter or exit
   // the mode as needed.
   void EnterOrExitLowPowerModeIfNeeded();
 
   // The main fullscreen window.
   base::scoped_nsobject<NSWindow> content_window_;
 
   // Weak, reset by WillLoseAcceleratedWidget before it goes away.
   ui::AcceleratedWidgetMac* widget_ = nullptr;
 
   // The window that we will put in front of the main fullscreen window when we
   // can.
   base::scoped_nsobject<FullscreenLowPowerWindow> low_power_window_;
 
   // Don't use the fullscreen low power window until we have completely
   // transitioned to low power mode.
   bool allowed_by_fullscreen_transition_ = false;
 
-  // Set by the AcceleratedWidgetHost with each frame. This must be true for
-  // 15 consecutive frames to enter low power mode (this is to ensure that the
-  // low power window has actually updated to the correct content before it
-  // appears).
-  uint64_t low_power_layer_valid_frame_count_ = 0;
+  // Set by the AcceleratedWidgetHost with each frame to indicate if the low
+  // power layer's contents are valid.
+  bool low_power_layer_valid_ = false;
 
   // Set if the NSView hierarchy allows low power mode. Low power mode is only
   // allowed when nothing but the web contents is on-screen.
   bool allowed_by_nsview_layout_ = true;
 
   // Set if there are no NSWindows that would be covered by the fullscreen low
   // power window.
   bool allowed_by_child_windows_ = false;
 
   // Set if there are no sheets (modal dialogues) that would be covered by the
   // fullscreen low power window.
   bool allowed_by_active_sheet_ = false;
 
   // Updated by EnterOrExitLowPowerModeIfNeeded.
-  bool in_low_power_mode_ = false;
+  enum State {
+    // The fullscreen low power window is hidden behind the main window.
+    Disabled,
+    // The fullscreen low power window is still hidden, but is counting up
+    // transition frames before showing itself.
+    WarmingUp,
+    // The fullscreen low power window is in front of the main window.
+    Enabled,
+  };
+  State state_ = Disabled;
+  uint64_t frames_in_state_ = 0;
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_FULLSCREEN_LOW_POWER_COORDINATOR_H_