Initialize an MTA on the Device Polling Thread

The change explicitly initializes a COM MTA on the device polling
thread. Previously, an COM implicitly initialized an MTA on the first
CoCreateInstance call.

BUG=734706

Change-Id: I64e70f06b2e82520419ce74e3bc2db396896af4c
Reviewed-on: https://chromium-review.googlesource.com/544685Reviewed-by: Tim Volodine <timvolodine@chromium.org>
Commit-Queue: Robert Liao <robliao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#481942}

device/sensors/data_fetcher_shared_memory_base.cc

@@ -15,6 +15,7 @@
 #include "base/stl_util.h"
 #include "base/threading/thread.h"
 #include "base/timer/timer.h"
+#include "build/build_config.h"
 #include "device/sensors/public/cpp/device_motion_hardware_buffer.h"
 #include "device/sensors/public/cpp/device_orientation_hardware_buffer.h"
 
@@ -193,6 +194,10 @@ bool DataFetcherSharedMemoryBase::InitAndStartPollingThreadIfNecessary() {
 
   polling_thread_.reset(new PollingThread("Device Sensor poller", this));
 
+#if defined(OS_WIN)
+  polling_thread_->init_com_with_mta(true);
+#endif
+
   if (!polling_thread_->Start()) {
     LOG(ERROR) << "Failed to start sensor data polling thread";
     return false;