Fast path for ThreadSpecific for main thread on TLS-slow platforms

third_party/WebKit/Source/wtf/WTF.cpp

Index: third_party/WebKit/Source/wtf/WTF.cpp
diff --git a/third_party/WebKit/Source/wtf/WTF.cpp b/third_party/WebKit/Source/wtf/WTF.cpp
index 5fb8a67f95cad7069ca53aa39a91f07a789fc395..a89c04ce9b254d18e2988d8d0dd124bb49ca94e0 100644
--- a/third_party/WebKit/Source/wtf/WTF.cpp
+++ b/third_party/WebKit/Source/wtf/WTF.cpp
@@ -33,6 +33,7 @@
 #include "wtf/Assertions.h"
 #include "wtf/Functional.h"
 #include "wtf/Threading.h"
+#include "wtf/WTFThreadData.h"
 #include "wtf/allocator/Partitions.h"
 #include "wtf/text/AtomicString.h"
 #include "wtf/text/StringStatics.h"
@@ -45,7 +46,6 @@ extern void initializeThreading();
 bool s_initialized;
 bool s_shutdown;
 void (*s_callOnMainThreadFunction)(MainThreadFunction, void*);
-ThreadIdentifier s_mainThreadIdentifier;
 
 namespace internal {
 
@@ -56,7 +56,7 @@ void callOnMainThread(MainThreadFunction* function, void* context) {
 }  // namespace internal
 
 bool isMainThread() {
-  return currentThread() == s_mainThreadIdentifier;
+  return WTFThreadData::isMainThread();
 }
 
 void initialize(void (*callOnMainThreadFunction)(MainThreadFunction, void*)) {
@@ -68,7 +68,6 @@ void initialize(void (*callOnMainThreadFunction)(MainThreadFunction, void*)) {
   initializeThreading();
 
   s_callOnMainThreadFunction = callOnMainThreadFunction;
-  s_mainThreadIdentifier = currentThread();
   AtomicString::init();
   StringStatics::init();
 }