Introduce new constructor to PlatformThread.

webrtc/modules/video_coding/frame_buffer2_unittest.cc

Index: webrtc/modules/video_coding/frame_buffer2_unittest.cc
diff --git a/webrtc/modules/video_coding/frame_buffer2_unittest.cc b/webrtc/modules/video_coding/frame_buffer2_unittest.cc
index 1761f588a2b41c9f37bc9516ac457d490b4c8f13..ebadafa883dcdf650cc5c2ecb84b75483d0fbcb1 100644
--- a/webrtc/modules/video_coding/frame_buffer2_unittest.cc
+++ b/webrtc/modules/video_coding/frame_buffer2_unittest.cc
@@ -163,7 +163,7 @@ class TestFrameBuffer2 : public ::testing::Test {
     ASSERT_FALSE(frames_[index]);
   }
 
-  static bool ExtractLoop(void* obj) {
+  static void ExtractLoop(void* obj) {
     TestFrameBuffer2* tfb = static_cast<TestFrameBuffer2*>(obj);
     while (true) {
       tfb->trigger_extract_event_.Wait(rtc::Event::kForever);
@@ -171,7 +171,7 @@ class TestFrameBuffer2 : public ::testing::Test {
         rtc::CritScope lock(&tfb->crit_);
         tfb->crit_acquired_event_.Set();
         if (tfb->tear_down_)
-          return false;
+          return;
 
         std::unique_ptr<FrameObject> frame;
         FrameBuffer::ReturnReason res =