Separate ResizeHelper from RenderWidgetHelper

content/browser/renderer_host/render_widget_resize_helper_mac.cc

+#include "content/browser/renderer_host/render_widget_resize_helper_mac.h"

[piman, 2014/07/15 19:56:00]

nit: copyright header needed.

[ccameron, 2014/07/15 20:36:24]

Done.

+
+#include "content/browser/gpu/gpu_process_host_ui_shim.h"
+#include "content/browser/renderer_host/render_process_host_impl.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace content {
+namespace {
+base::LazyInstance<RenderWidgetResizeHelper> g_render_widget_task_runner;
+}  // namespace
+
+// A helper used with DidReceiveBackingStoreMsg that we hold a pointer to in
+// pending_paints_.

[piman, 2014/07/15 19:56:00]

nit: fix comment.

[ccameron, 2014/07/15 20:36:24]

Done.

+class RenderWidgetResizeHelper::EnqueuedTask {
+ public:
+  enum Type {
+    RENDERER_IPC,
+    GPU_IPC,
+  };
+  EnqueuedTask(Type type, int process_id, const IPC::Message& m);
+  ~EnqueuedTask();
+  void Run();
+
+ private:
+  Type type_;
+  int process_id_;
+  IPC::Message message_;
+  bool has_run_;
+
+  DISALLOW_COPY_AND_ASSIGN(EnqueuedTask);
+};
+
+RenderWidgetResizeHelper::EnqueuedTask::EnqueuedTask(
+    Type type,
+    int process_id,
+    const IPC::Message& m)
+    : type_(type),
+      process_id_(process_id),
+      message_(m),
+      has_run_(false) {
+}
+
+RenderWidgetResizeHelper::EnqueuedTask::~EnqueuedTask() {
+}
+
+void RenderWidgetResizeHelper::EnqueuedTask::Run() {
+  if (has_run_)
+    return;
+
+  RenderWidgetResizeHelper::Get()->WillRunEnqueuedTask(this);
+  has_run_ = true;
+
+  switch (type_) {
+    case RENDERER_IPC: {
+      RenderProcessHost* host = RenderProcessHost::FromID(process_id_);
+      if (host)
+        host->OnMessageReceived(message_);
+    } break;

[piman, 2014/07/15 19:56:00]

nit: break inside the {}

[ccameron, 2014/07/15 20:36:24]

Done.

+    case GPU_IPC: {
+      GpuProcessHostUIShim* host = GpuProcessHostUIShim::FromID(process_id_);
+      if (host)
+        host->OnMessageReceived(message_);
+    } break;

[piman, 2014/07/15 19:56:00]

nit: here too.

[ccameron, 2014/07/15 20:36:24]

Done.

+  }
+}
+
+// static
+RenderWidgetResizeHelper* RenderWidgetResizeHelper::Get() {
+  return g_render_widget_task_runner.Pointer();
+}
+
+bool RenderWidgetResizeHelper::WaitForSingleTaskToRun(
+    const base::TimeDelta& max_delay) {
+  base::TimeTicks time_start = base::TimeTicks::Now();
+
+  for (;;) {
+    // Peek at the message from the front of the queue. Running it will remove
+    // it from the queue.
+    EnqueuedTask* task = NULL;
+    {
+      base::AutoLock lock(task_queue_lock_);
+      if (!task_queue_.empty())
+        task = task_queue_.front();
+    }
+
+    if (task) {
+      task->Run();
+      return true;
+    }
+
+    // Calculate the maximum amount of time that we are willing to sleep.
+    base::TimeDelta max_sleep_time =
+        max_delay - (base::TimeTicks::Now() - time_start);
+    if (max_sleep_time <= base::TimeDelta::FromMilliseconds(0))
+      break;
+
+    base::ThreadRestrictions::ScopedAllowWait allow_wait;
+    event_.TimedWait(max_sleep_time);
+  }
+
+  return false;
+}
+
+void RenderWidgetResizeHelper::PostEnqueuedTask(EnqueuedTask* task) {
+  {
+    base::AutoLock lock(task_queue_lock_);
+    task_queue_.push_back(task);
+  }
+
+  // Notify anyone waiting on the UI thread that there is a new entry in the
+  // task map.  If they don't find the entry they are looking for, then they
+  // will just continue waiting.
+  event_.Signal();
+
+  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+      base::Bind(&EnqueuedTask::Run, base::Owned(task)));
+}
+
+void RenderWidgetResizeHelper::WillRunEnqueuedTask(EnqueuedTask* task) {
+  base::AutoLock lock(task_queue_lock_);
+  DCHECK(task_queue_.front() == task);
+  task_queue_.pop_front();
+}
+
+void RenderWidgetResizeHelper::PostRendererProcessMsg(
+    int render_process_id, const IPC::Message& msg) {
+  PostEnqueuedTask(new EnqueuedTask(
+      EnqueuedTask::RENDERER_IPC, render_process_id, msg));
+}
+
+void RenderWidgetResizeHelper::PostGpuProcessMsg(
+    int gpu_host_id, const IPC::Message& msg) {
+  PostEnqueuedTask(new EnqueuedTask(EnqueuedTask::GPU_IPC, gpu_host_id, msg));
+}
+
+RenderWidgetResizeHelper::RenderWidgetResizeHelper()
+#if defined(OS_WIN)
+    : event_(CreateEvent(NULL, FALSE /* auto-reset */, FALSE, NULL)) {}
+#elif defined(OS_POSIX)
+    : event_(false /* auto-reset */, false) {}

[piman, 2014/07/15 19:56:00]

nit: why not always this path on all platforms? It is equivalent afaict.

[ccameron, 2014/07/15 20:36:25]

This is from the earlier versions of the code -- not sure what this distinction
is.

[piman, 2014/07/15 22:49:36]

This probably predates some API unification.
Reading waitable_event_win.cc, the constructor would do exactly the same thing.
Let's just use the cross-platform constructor?

+#endif
+
+RenderWidgetResizeHelper::~RenderWidgetResizeHelper() {
+  // The elements of task_queue_ will call back into this object, so we
+  // should not be destroyed unless task_queue_ is empty!
+  DCHECK(task_queue_.empty());
+}
+
+}  // namespace content
+