Ping watchdog thread during GpuChannel destruction

gpu/ipc/service/gpu_command_buffer_stub.cc

Index: gpu/ipc/service/gpu_command_buffer_stub.cc
diff --git a/gpu/ipc/service/gpu_command_buffer_stub.cc b/gpu/ipc/service/gpu_command_buffer_stub.cc
index 412d9a97182600dd249a90304302123b615ba887..81494b5a7d873f67e74dd04ed69dd8e5e45f4b56 100644
--- a/gpu/ipc/service/gpu_command_buffer_stub.cc
+++ b/gpu/ipc/service/gpu_command_buffer_stub.cc
@@ -26,6 +26,7 @@
 #include "gpu/command_buffer/service/logger.h"
 #include "gpu/command_buffer/service/mailbox_manager.h"
 #include "gpu/command_buffer/service/memory_tracking.h"
+#include "gpu/command_buffer/service/progress_reporter.h"
 #include "gpu/command_buffer/service/query_manager.h"
 #include "gpu/command_buffer/service/sync_point_manager.h"
 #include "gpu/command_buffer/service/transfer_buffer_manager.h"
@@ -105,6 +106,24 @@ class GpuCommandBufferMemoryTracker : public gles2::MemoryTracker {
   DISALLOW_COPY_AND_ASSIGN(GpuCommandBufferMemoryTracker);
 };
 
+// GpuCommandBufferProgressReporter is used as a bridge between the
+// ContextGroup and the GpuChannel's GpuWatchdogThread.
+class GpuCommandBufferProgressReporter : public gles2::ProgressReporter {
+ public:
+  GpuCommandBufferProgressReporter(GpuChannel* channel) : channel_(channel) {}
+
+  void ReportProgress() override {
+    if (auto* watchdog = channel_->watchdog()) {

[danakj, 2016/10/05 01:53:48]

when is it null?

[ericrk, 2016/10/05 18:07:32]

added stub and removed.

+      watchdog->CheckArmed();
+    }
+  }
+
+ private:
+  // The GpuChannel always outlives the GpuCommandBufferStub and the
+  // ContextGroups it creates, so it's safe to hold by raw pointer here.
+  GpuChannel* channel_;
+};
+
 // FastSetActiveURL will shortcut the expensive call to SetActiveURL when the
 // url_hash matches.
 void FastSetActiveURL(const GURL& url, size_t url_hash, GpuChannel* channel) {
@@ -469,7 +488,8 @@ bool GpuCommandBufferStub::Initialize(
         manager->shader_translator_cache(),
         manager->framebuffer_completeness_cache(), feature_info,
         init_params.attribs.bind_generates_resource,
-        gmb_factory ? gmb_factory->AsImageFactory() : nullptr);
+        gmb_factory ? gmb_factory->AsImageFactory() : nullptr,
+        base::MakeUnique<GpuCommandBufferProgressReporter>(channel_));

[danakj, 2016/10/05 01:53:48]

I was surprised at the ownership model here. I would normally expect this
relationship to be: GpuCommandBufferStub is/owns a ProgressReporter and passes a
raw pointer here. Why'd you go with a memory alloc/uniqueptr/passing ownership
of a raw pointer (the channel_) back here?

[ericrk, 2016/10/05 18:07:31]

I agree, this was a weird decision - I was originally thinking this reduced the
modifications to stub, but in retrospect this didn't really pan out and makes
the ownership / lifetime less clear. Made the stub a ProgressReporter, which
makes things cleaner.

   }
 
 #if defined(OS_MACOSX)