Add a delay to clear GL context when app is backgrounded

A common behavior on Android is for the user to press home or recents
button accidently and get back to the app. This behavior would cause
Chrome to clear the contexts and recreate which is a waste of time. So,
add a 5 second delay before clearing the context.
As a side effect, this delay also considerably lowers the risk of the
renderers initializing the GPU command buffer after clearing since they
usually receive the "not-visible" message within 5 seconds.

BUG=725303

Change-Id: I7d2655c75b66cf073b82c270baa3f1f3b27b3a8a
Reviewed-on: https://chromium-review.googlesource.com/571294
Commit-Queue: Siddhartha S <ssid@chromium.org>
Reviewed-by: Maria Khomenko <mariakhomenko@chromium.org>
Reviewed-by: Eric Karl <ericrk@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487539}

gpu/ipc/service/gpu_channel_manager.cc

@@ -78,6 +78,7 @@ GpuChannelManager::GpuChannelManager(
           base::Bind(&GpuChannelManager::OnApplicationStateChange,
                      base::Unretained(this))),
       is_running_on_low_end_mode_(base::SysInfo::IsLowEndDevice()),
+      is_backgrounded_for_testing_(false),
 #endif
       exiting_for_lost_context_(false),
       activity_flags_(std::move(activity_flags)),
@@ -258,13 +259,31 @@ void GpuChannelManager::OnApplicationStateChange(
     return;
   }
 
-  if (!task_runner_->BelongsToCurrentThread()) {
-    task_runner_->PostTask(
-        FROM_HERE, base::Bind(&GpuChannelManager::OnApplicationStateChange,
-                              weak_factory_.GetWeakPtr(), state));
+  // Clear the GL context on low-end devices after a 5 second delay, so that we
+  // don't clear in case the user pressed the home or recents button by mistake
+  // and got back to Chrome quickly.
+  const int64_t kDelayToClearContextMs = 5000;
+
+  task_runner_->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&GpuChannelManager::OnApplicationBackgrounded,
+                 weak_factory_.GetWeakPtr()),
+      base::TimeDelta::FromMilliseconds(kDelayToClearContextMs));
+  return;
+}
+
+void GpuChannelManager::OnApplicationBackgrounded() {
+  // Check if the app is still in background after the delay.
+  auto state = base::android::ApplicationStatusListener::GetState();
+  if (state != base::android::APPLICATION_STATE_HAS_STOPPED_ACTIVITIES &&
+      state != base::android::APPLICATION_STATE_HAS_DESTROYED_ACTIVITIES &&
+      !is_backgrounded_for_testing_) {
     return;
   }
 
+  if (!is_running_on_low_end_mode_)
+    return;
+
   // Delete all the GL contexts when the channel does not use WebGL and Chrome
   // goes to background on low-end devices.
   std::vector<int> channels_to_clear;

gpu/ipc/service/gpu_channel_manager.h

@@ -145,12 +145,16 @@ class GPU_EXPORT GpuChannelManager {
   SyncPointManager* sync_point_manager() const { return sync_point_manager_; }
 
  private:
+  friend class GpuChannelManagerTest;
+
   void InternalDestroyGpuMemoryBuffer(gfx::GpuMemoryBufferId id, int client_id);
   void InternalDestroyGpuMemoryBufferOnIO(gfx::GpuMemoryBufferId id,
                                           int client_id);
 #if defined(OS_ANDROID)
   void ScheduleWakeUpGpu();
   void DoWakeUpGpu();
+
+  void OnApplicationBackgrounded();
 #endif
 
   void HandleMemoryPressure(
@@ -195,6 +199,7 @@ class GPU_EXPORT GpuChannelManager {
 
   base::android::ApplicationStatusListener application_status_listener_;
   bool is_running_on_low_end_mode_;
+  bool is_backgrounded_for_testing_;
 #endif
 
   // Set during intentional GPU process shutdown.

gpu/ipc/service/gpu_channel_manager_unittest.cc

@@ -47,8 +47,8 @@ class GpuChannelManagerTest : public GpuChannelTestCommon {
     GpuCommandBufferStub* stub = channel->LookupCommandBuffer(kRouteId);
     EXPECT_TRUE(stub);
 
-    channel_manager()->OnApplicationStateChange(
-        base::android::APPLICATION_STATE_HAS_STOPPED_ACTIVITIES);
+    channel_manager()->is_backgrounded_for_testing_ = true;
+    channel_manager()->OnApplicationBackgrounded();
     stub = channel->LookupCommandBuffer(kRouteId);
     if (should_clear_stub) {
       EXPECT_FALSE(stub);