[Chromecast] Fix uninitialized variable in loopback handler

Bug: internal b/138645210
Change-Id: I9de9df6663290767bcb4657a9f8e7cd09346fea8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1726629Reviewed-by: Sergey Volk <servolk@chromium.org>
Commit-Queue: Kenneth MacKay <kmackay@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682355}

chromecast/media/cma/backend/loopback_handler.cc

@@ -239,6 +239,7 @@ class LoopbackHandlerImpl : public LoopbackHandler,
     lock_.AssertAcquired();
 
     if (tasks_.size() == kMaxTasks) {
+      task_signal_.Signal();
       return;
     }
     tasks_.emplace_back(0, kSampleFormatF32, 0, 0, 0, nullptr, 0);
@@ -306,7 +307,7 @@ class LoopbackHandlerImpl : public LoopbackHandler,
   base::Lock lock_;
   uint32_t buffer_tag_ GUARDED_BY(lock_) = 0;
   std::vector<std::unique_ptr<uint8_t[]>> buffers_ GUARDED_BY(lock_);
-  bool stop_thread_ GUARDED_BY(lock_);
+  bool stop_thread_ GUARDED_BY(lock_) = false;
   base::ConditionVariable task_signal_;
 
   std::vector<Task> tasks_;