Specify TaskType of posted Task explicitly in Sensor API

The spec specifies its own Sensor task source.
https://w3c.github.io/sensors/#the-sensor-interface

BUG=624696

Review-Url: https://codereview.chromium.org/2587733002
Cr-Commit-Position: refs/heads/master@{#439430}

third_party/WebKit/Source/core/dom/TaskRunnerHelper.cpp

@@ -30,6 +30,7 @@ WebTaskRunner* TaskRunnerHelper::get(TaskType type, LocalFrame* frame) {
     case TaskType::FileReading:
     case TaskType::DatabaseAccess:
     case TaskType::Presentation:
+    case TaskType::Sensor:
     case TaskType::Timer:
     case TaskType::Internal:
     case TaskType::Unspecified:

third_party/WebKit/Source/core/dom/TaskRunnerHelper.h

@@ -36,6 +36,7 @@ enum class TaskType : unsigned {
   FileReading,
   DatabaseAccess,
   Presentation,
+  Sensor,
 
   // Other internal tasks that cannot fit any of the above task runners
   // can be posted here, but the usage is not encouraged. The task runner

third_party/WebKit/Source/modules/sensor/Sensor.cpp

@@ -7,6 +7,7 @@
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/ExecutionContextTask.h"
+#include "core/dom/TaskRunnerHelper.h"
 #include "core/inspector/ConsoleMessage.h"
 #include "device/generic_sensor/public/interfaces/sensor.mojom-blink.h"
 #include "modules/sensor/SensorErrorEvent.h"
@@ -265,7 +266,7 @@ void Sensor::onSensorUpdateNotification() {
   if (getExecutionContext() &&
       m_sensorProxy->sensorReading()->isReadingUpdated(m_storedData)) {
     getExecutionContext()->postTask(
-        BLINK_FROM_HERE,
+        TaskType::Sensor, BLINK_FROM_HERE,
         createSameThreadTask(&Sensor::notifySensorReadingChanged,
                              wrapWeakPersistent(this)));
   }
@@ -280,7 +281,8 @@ void Sensor::updateState(Sensor::SensorState newState) {
   if (newState == SensorState::Activated && getExecutionContext()) {
     DCHECK_EQ(SensorState::Activating, m_state);
     getExecutionContext()->postTask(
-        BLINK_FROM_HERE, createSameThreadTask(&Sensor::notifyOnActivate,
+        TaskType::Sensor, BLINK_FROM_HERE,
+        createSameThreadTask(&Sensor::notifyOnActivate,
                              wrapWeakPersistent(this)));
   }
 
@@ -295,7 +297,7 @@ void Sensor::reportError(ExceptionCode code,
     auto error =
         DOMException::create(code, sanitizedMessage, unsanitizedMessage);
     getExecutionContext()->postTask(
-        BLINK_FROM_HERE,
+        TaskType::Sensor, BLINK_FROM_HERE,
         createSameThreadTask(&Sensor::notifyError, wrapWeakPersistent(this),
                              wrapPersistent(error)));
   }