Worker: Rename WorkletThreadHolder::threadHolderInstance() to getInstance()

This was raised in https://codereview.chromium.org/2582483002/#msg9

getInstance() would be more common name for a function to get a singleton
instance and less confusing for code readers.

BUG=n/a

Review-Url: https://codereview.chromium.org/2579823002
Cr-Commit-Position: refs/heads/master@{#438984}

third_party/WebKit/Source/core/workers/ThreadedWorkletTest.cpp

@@ -28,8 +28,8 @@ class ThreadedWorkletThreadForTest : public WorkerThread {
   ~ThreadedWorkletThreadForTest() override{};
 
   WorkerBackingThread& workerBackingThread() override {
-    auto workletThreadHolder = WorkletThreadHolder<
-        ThreadedWorkletThreadForTest>::threadHolderInstance();
+    auto workletThreadHolder =
+        WorkletThreadHolder<ThreadedWorkletThreadForTest>::getInstance();
     DCHECK(workletThreadHolder);
     return *workletThreadHolder->thread();
   }

third_party/WebKit/Source/core/workers/WorkletThreadHolder.h

@@ -19,7 +19,7 @@ namespace blink {
 template <class DerivedWorkletThread>
 class WorkletThreadHolder {
  public:
-  static WorkletThreadHolder<DerivedWorkletThread>* threadHolderInstance() {
+  static WorkletThreadHolder<DerivedWorkletThread>* getInstance() {
     MutexLocker locker(holderInstanceMutex());
     return s_threadHolderInstance;
   }

third_party/WebKit/Source/modules/compositorworker/AbstractAnimationWorkletThread.cpp

@@ -25,8 +25,7 @@ AbstractAnimationWorkletThread::AbstractAnimationWorkletThread(
 AbstractAnimationWorkletThread::~AbstractAnimationWorkletThread() {}
 
 WorkerBackingThread& AbstractAnimationWorkletThread::workerBackingThread() {
-  return *WorkletThreadHolder<
-              AbstractAnimationWorkletThread>::threadHolderInstance()
+  return *WorkletThreadHolder<AbstractAnimationWorkletThread>::getInstance()
               ->thread();
 }
 
@@ -38,12 +37,11 @@ void collectAllGarbageOnThread(WaitableEvent* doneEvent) {
 void AbstractAnimationWorkletThread::collectAllGarbage() {
   DCHECK(isMainThread());
   WaitableEvent doneEvent;
-  WorkletThreadHolder<AbstractAnimationWorkletThread>* threadHolderInstance =
-      WorkletThreadHolder<
-          AbstractAnimationWorkletThread>::threadHolderInstance();
-  if (!threadHolderInstance)
+  WorkletThreadHolder<AbstractAnimationWorkletThread>* workletThreadHolder =
+      WorkletThreadHolder<AbstractAnimationWorkletThread>::getInstance();
+  if (!workletThreadHolder)
     return;
-  threadHolderInstance->thread()->backingThread().postTask(
+  workletThreadHolder->thread()->backingThread().postTask(
       BLINK_FROM_HERE, crossThreadBind(&collectAllGarbageOnThread,
                                        crossThreadUnretained(&doneEvent)));
   doneEvent.wait();

third_party/WebKit/Source/modules/webaudio/AudioWorkletThread.cpp

@@ -39,8 +39,7 @@ AudioWorkletThread::AudioWorkletThread(
 AudioWorkletThread::~AudioWorkletThread() {}
 
 WorkerBackingThread& AudioWorkletThread::workerBackingThread() {
-  return *WorkletThreadHolder<AudioWorkletThread>::threadHolderInstance()
-              ->thread();
+  return *WorkletThreadHolder<AudioWorkletThread>::getInstance()->thread();
 }
 
 void collectAllGarbageOnAudioWorkletThread(WaitableEvent* doneEvent) {
@@ -51,11 +50,11 @@ void collectAllGarbageOnAudioWorkletThread(WaitableEvent* doneEvent) {
 void AudioWorkletThread::collectAllGarbage() {
   DCHECK(isMainThread());
   WaitableEvent doneEvent;
-  WorkletThreadHolder<AudioWorkletThread>* threadHolderInstance =
-      WorkletThreadHolder<AudioWorkletThread>::threadHolderInstance();
-  if (!threadHolderInstance)
+  WorkletThreadHolder<AudioWorkletThread>* workletThreadHolder =
+      WorkletThreadHolder<AudioWorkletThread>::getInstance();
+  if (!workletThreadHolder)
     return;
-  threadHolderInstance->thread()->backingThread().postTask(
+  workletThreadHolder->thread()->backingThread().postTask(
       BLINK_FROM_HERE, crossThreadBind(&collectAllGarbageOnAudioWorkletThread,
                                        crossThreadUnretained(&doneEvent)));
   doneEvent.wait();