Big patch to implement Chromium-side of Gamepad support

content/browser/gamepad/gamepad_provider.cc

Index: content/browser/gamepad/gamepad_provider.cc
diff --git a/content/browser/gamepad/gamepad_provider.cc b/content/browser/gamepad/gamepad_provider.cc
index c8eed65a30f00b447a888bfa75eedf7932c9f521..80ca1a6f4636f60cf6492d251f2994fa0bb0b563 100644
--- a/content/browser/gamepad/gamepad_provider.cc
+++ b/content/browser/gamepad/gamepad_provider.cc
@@ -9,6 +9,7 @@
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop.h"
+#include "base/synchronization/lock.h"
 #include "base/task.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_restrictions.h"
@@ -23,8 +24,6 @@
 
 namespace content {
 
-GamepadProvider* GamepadProvider::instance_ = NULL;
-
 // Define the default data fetcher that GamepadProvider will use if none is
 // supplied. (GamepadPlatformDataFetcher).
 #if defined(OS_WIN)
@@ -44,9 +43,10 @@ typedef GamepadEmptyDataFetcher GamepadPlatformDataFetcher;
 #endif
 
 GamepadProvider::GamepadProvider(GamepadDataFetcher* fetcher)
-    : creator_loop_(MessageLoop::current()->message_loop_proxy()),
-      provided_fetcher_(fetcher),
+    : is_paused_(false),
       devices_changed_(true),
+      creator_loop_(MessageLoop::current()->message_loop_proxy()),
+      provided_fetcher_(fetcher),
       ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)) {
   size_t data_size = sizeof(GamepadHardwareBuffer);
   base::SystemMonitor* monitor = base::SystemMonitor::Get();
@@ -55,13 +55,29 @@ GamepadProvider::GamepadProvider(GamepadDataFetcher* fetcher)
   gamepad_shared_memory_.CreateAndMapAnonymous(data_size);
   GamepadHardwareBuffer* hwbuf = SharedMemoryAsHardwareBuffer();
   memset(hwbuf, 0, sizeof(GamepadHardwareBuffer));
+
+  DCHECK(MessageLoop::current()->message_loop_proxy() == creator_loop_);
+
+  polling_thread_.reset(new base::Thread("Gamepad polling thread"));
+  if (!polling_thread_->Start()) {
+    LOG(ERROR) << "Failed to start gamepad polling thread";
+    polling_thread_.reset();
+    return;
+  }
+
+  MessageLoop* polling_loop = polling_thread_->message_loop();
+  polling_loop->PostTask(
+      FROM_HERE,
+      base::Bind(&GamepadProvider::DoInitializePollingThread, this));
 }
 
 GamepadProvider::~GamepadProvider() {
   base::SystemMonitor* monitor = base::SystemMonitor::Get();
   if (monitor)
     monitor->RemoveDevicesChangedObserver(this);
-  Stop();
+
+  polling_thread_.reset();
+  data_fetcher_.reset();
 }
 
 base::SharedMemoryHandle GamepadProvider::GetRendererSharedMemoryHandle(
@@ -71,34 +87,27 @@ base::SharedMemoryHandle GamepadProvider::GetRendererSharedMemoryHandle(
   return renderer_handle;
 }
 
-void GamepadProvider::OnDevicesChanged() {
-  devices_changed_ = true;
+void GamepadProvider::Pause() {
+  base::AutoLock lock(is_paused_lock_);
+  is_paused_ = true;
 }
 
-void GamepadProvider::Start() {
-  DCHECK(MessageLoop::current()->message_loop_proxy() == creator_loop_);
+void GamepadProvider::Resume() {
+  base::AutoLock lock(is_paused_lock_);
 
-  if (polling_thread_.get())
+  if (!is_paused_)
     return;
 
-  polling_thread_.reset(new base::Thread("Gamepad polling thread"));
-  if (!polling_thread_->Start()) {
-    LOG(ERROR) << "Failed to start gamepad polling thread";
-    polling_thread_.reset();
-    return;
-  }
-
+  is_paused_ = false;
   MessageLoop* polling_loop = polling_thread_->message_loop();
   polling_loop->PostTask(
       FROM_HERE,
-      base::Bind(&GamepadProvider::DoInitializePollingThread, this));
+      base::Bind(&GamepadProvider::ScheduleDoPoll, this));
 }
 
-void GamepadProvider::Stop() {
-  DCHECK(MessageLoop::current()->message_loop_proxy() == creator_loop_);
-
-  polling_thread_.reset();
-  data_fetcher_.reset();
+void GamepadProvider::OnDevicesChanged() {
+  base::AutoLock lock(devices_changed_lock_);
+  devices_changed_ = true;
 }
 
 void GamepadProvider::DoInitializePollingThread() {
@@ -123,18 +132,27 @@ void GamepadProvider::DoPoll() {
       sizeof(WebKit::WebGamepads),
       "Racey reads are discarded");
 
+  devices_changed_lock_.Acquire();
+
   // Acquire the SeqLock. There is only ever one writer to this data.
   // See gamepad_hardware_buffer.h.
   hwbuf->sequence.WriteBegin();
   data_fetcher_->GetGamepadData(&hwbuf->buffer, devices_changed_);
   hwbuf->sequence.WriteEnd();
   devices_changed_ = false;
+
+  devices_changed_lock_.Release();
+
   // Schedule our next interval of polling.
   ScheduleDoPoll();
 }
 
 void GamepadProvider::ScheduleDoPoll() {
   DCHECK(MessageLoop::current() == polling_thread_->message_loop());
+  base::AutoLock lock(is_paused_lock_);
+
+  if (is_paused_)
+    return;
 
   MessageLoop::current()->PostDelayedTask(
       FROM_HERE,