Allow Thread to initialize COM for Windows consumers who need it

base/threading/thread.h

Index: base/threading/thread.h
===================================================================
--- base/threading/thread.h	(revision 162015)
+++ base/threading/thread.h	(working copy)
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef BASE_THREAD_H_
-#define BASE_THREAD_H_
+#ifndef BASE_THREADING_THREAD_H_
+#define BASE_THREADING_THREAD_H_
 
 #include <string>
 
@@ -12,8 +12,18 @@
 #include "base/message_loop_proxy.h"
 #include "base/threading/platform_thread.h"
 
+#if defined(OS_WIN)
+#include "base/memory/scoped_ptr.h"
+#endif
+
 namespace base {
 
+#if defined(OS_WIN)
+namespace win {
+class ScopedCOMInitializer;
+}
+#endif
+
 // A simple thread abstraction that establishes a MessageLoop on a new thread.
 // The consumer uses the MessageLoop of the thread to cause code to execute on
 // the thread.  When this object is destroyed the thread is terminated.  All
@@ -57,6 +67,18 @@
   // before it is destructed.
   virtual ~Thread();
 
+#if defined(OS_WIN)
+  // Causes the thread to initialize COM.  This must be called before calling
+  // Start() or StartWithOptions().  If |use_mta| is false, the thread is also
+  // started with a TYPE_UI message loop.  It is an error to call
+  // init_com_with_mta(false) and then StartWithOptions() with any message loop
+  // type other than TYPE_UI.
+  void init_com_with_mta(bool use_mta) {
+    DCHECK(!started_);
+    com_status_ = use_mta ? MTA : STA;
+  }
+#endif
+
   // Starts the thread.  Returns true if the thread was successfully started;
   // otherwise, returns false.  Upon successful return, the message_loop()
   // getter will return non-null.
@@ -148,7 +170,15 @@
   }
 
  private:
-  bool thread_was_started() const { return started_; }
+#if defined(OS_WIN)
+  enum ComStatus {
+    NONE,
+    STA,
+    MTA,
+  };
+  ComStatus com_status_;
+  scoped_ptr<win::ScopedCOMInitializer> com_initializer_;
+#endif
 
   // PlatformThread::Delegate methods:
   virtual void ThreadMain() OVERRIDE;
@@ -187,4 +217,4 @@
 
 }  // namespace base
 
-#endif  // BASE_THREAD_H_
+#endif  // BASE_THREADING_THREAD_H_