Disable COM Initialization on SchedulerWorkers When COM_INIT_CHECK_HOOK_ENABLED()

This change will allow for the detection of tasks running in
TaskScheduler that fail to post their task in a COM STA Task Runner
instead.

BUG=706512

Change-Id: If8ea9df63cface0dc48aa11b5254ab3e6d87dc4f
Reviewed-on: https://chromium-review.googlesource.com/549223
Commit-Queue: Robert Liao <robliao@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487269}

base/task_scheduler/scheduler_worker.cc

@@ -15,6 +15,7 @@
 #if defined(OS_MACOSX)
 #include "base/mac/scoped_nsautorelease_pool.h"
 #elif defined(OS_WIN)
+#include "base/win/com_init_check_hook.h"
 #include "base/win/scoped_com_initializer.h"
 #endif
 
@@ -43,7 +44,10 @@ class SchedulerWorker::Thread : public PlatformThread::Delegate {
     // A SchedulerWorker starts out waiting for work.
     outer_->delegate_->WaitForWork(&wake_up_event_);
 
-#if defined(OS_WIN)
+    // When defined(COM_INIT_CHECK_HOOK_ENABLED), ignore
+    // SchedulerBackwardCompatibility::INIT_COM_STA to find incorrect uses of
+    // COM that should be running in a COM STA Task Runner.
+#if defined(OS_WIN) && !defined(COM_INIT_CHECK_HOOK_ENABLED)
     std::unique_ptr<win::ScopedCOMInitializer> com_initializer;
     if (outer_->backward_compatibility_ ==
         SchedulerBackwardCompatibility::INIT_COM_STA) {

base/task_scheduler/scheduler_worker_unittest.cc

@@ -30,6 +30,8 @@
 
 #if defined(OS_WIN)
 #include <objbase.h>
+
+#include "base/win/com_init_check_hook.h"
 #endif
 
 using testing::_;
@@ -931,7 +933,13 @@ TEST(TaskSchedulerWorkerTest, BackwardCompatibilityEnabled) {
 
   // The call to CoInitializeEx() should have returned S_FALSE to indicate that
   // the COM library was already initialized on the thread.
+  // See SchedulerWorker::Thread::ThreadMain for why we expect two different
+  // results here.
+#if defined(COM_INIT_CHECK_HOOK_ENABLED)
+  EXPECT_EQ(S_OK, delegate_raw->coinitialize_hresult());
+#else
   EXPECT_EQ(S_FALSE, delegate_raw->coinitialize_hresult());
+#endif
 
   worker->JoinForTesting();
 }