Reject outstanding promises asynchronously when cleared

media/base/cdm_promise_adapter.cc

Index: media/base/cdm_promise_adapter.cc
diff --git a/media/base/cdm_promise_adapter.cc b/media/base/cdm_promise_adapter.cc
index 5df17d861cbc00af784c6e79b8e7ab673bf8e83e..a9e189d1c4ce723ba3b152d55ffb082ababf0470 100644
--- a/media/base/cdm_promise_adapter.cc
+++ b/media/base/cdm_promise_adapter.cc
@@ -6,10 +6,18 @@
 
 #include <utility>
 
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/single_thread_task_runner.h"
+#include "base/thread_task_runner_handle.h"
 #include "media/base/media_keys.h"
 
 namespace media {
 
+static void AbortPromise(scoped_ptr<CdmPromise> promise) {
+  promise->reject(MediaKeys::UNKNOWN_ERROR, 0, "Operation aborted.");
+}
+
 CdmPromiseAdapter::CdmPromiseAdapter() : next_promise_id_(1) {
 }
 
@@ -60,10 +68,15 @@ void CdmPromiseAdapter::RejectPromise(uint32_t promise_id,
 }
 
 void CdmPromiseAdapter::Clear() {
-  // Reject all outstanding promises.
+  // Reject all outstanding promises asynchronously. This is done as it
+  // may be triggered by gc in blink, and it doesn't like executing code
+  // while gc is running.
   DCHECK(thread_checker_.CalledOnValidThread());
-  for (auto& promise : promises_)
-    promise.second->reject(MediaKeys::UNKNOWN_ERROR, 0, "Operation aborted.");
+  while (promises_.begin() != promises_.end()) {
+    scoped_ptr<CdmPromise> promise(promises_.take_and_erase(promises_.begin()));
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::Bind(&AbortPromise, base::Passed(&promise)));
+  }
   promises_.clear();
 }