Use TraceWrapperV8Reference to hold ExceptionState::exception_.

On-stack tracing of TraceWrapperV8Reference Just Works.

Bug: 1013149
Change-Id: I8c403cd4b9c86adb344fefbf32602d87d39eceb2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2625372Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843139}

third_party/blink/renderer/platform/bindings/exception_state.h

@@ -34,7 +34,7 @@
 #include "base/macros.h"
 #include "base/notreached.h"
 #include "third_party/blink/renderer/platform/bindings/exception_code.h"
-#include "third_party/blink/renderer/platform/bindings/scoped_persistent.h"
+#include "third_party/blink/renderer/platform/bindings/trace_wrapper_v8_reference.h"
 #include "third_party/blink/renderer/platform/bindings/v8_throw_exception.h"
 #include "third_party/blink/renderer/platform/platform_export.h"
 #include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
@@ -190,7 +190,7 @@ class PLATFORM_EXPORT ExceptionState {
   const char* interface_name_;
   // The exception is empty when it was thrown through
   // DummyExceptionStateForTesting.
-  ScopedPersistent<v8::Value> exception_;
+  TraceWrapperV8Reference<v8::Value> exception_;
   v8::Isolate* isolate_;
 
   DISALLOW_COPY_AND_ASSIGN(ExceptionState);