Cancel a task associated to TaskHandle when the TaskHandle is overridden

third_party/WebKit/Source/platform/WebTaskRunner.cpp

Index: third_party/WebKit/Source/platform/WebTaskRunner.cpp
diff --git a/third_party/WebKit/Source/platform/WebTaskRunner.cpp b/third_party/WebKit/Source/platform/WebTaskRunner.cpp
index 4fb10649a88da4ce844c7e6dfd73015a4f713924..059abdf83d05f66c7baf472599d312d4509ab646 100644
--- a/third_party/WebKit/Source/platform/WebTaskRunner.cpp
+++ b/third_party/WebKit/Source/platform/WebTaskRunner.cpp
@@ -71,7 +71,12 @@ TaskHandle::~TaskHandle() {
 }
 
 TaskHandle::TaskHandle(TaskHandle&&) = default;
-TaskHandle& TaskHandle::operator=(TaskHandle&&) = default;
+
+TaskHandle& TaskHandle::operator=(TaskHandle&& other) {
+  TaskHandle tmp(std::move(other));
+  m_runner.swap(tmp.m_runner);
+  return *this;
+}
 
 TaskHandle::TaskHandle(RefPtr<Runner> runner) : m_runner(std::move(runner)) {
   DCHECK(m_runner);