web-threads: Create a single instance of WebThread for each blink thread.

content/child/blink_platform_impl.cc

Index: content/child/blink_platform_impl.cc
diff --git a/content/child/blink_platform_impl.cc b/content/child/blink_platform_impl.cc
index f4d609b2f3f9535a0e352baac876888faba54a2b..eac44c4c7443fadb67d101c1434d96dca85f3323 100644
--- a/content/child/blink_platform_impl.cc
+++ b/content/child/blink_platform_impl.cc
@@ -13,7 +13,6 @@
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
-#include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/process/process_metrics.h"
@@ -418,7 +417,7 @@ BlinkPlatformImpl::BlinkPlatformImpl()
       shared_timer_fire_time_(0.0),
       shared_timer_fire_time_was_set_while_suspended_(false),
       shared_timer_suspended_(0),
-      current_thread_slot_(&DestroyCurrentThread) {
+      current_thread_slot_() {

[Sami, 2015/03/02 11:40:02]

nit: I don't think you need to initialize current_thread_slot_ explicitly
anymore (even though the constructor is explicit).

[sadrul, 2015/03/02 16:53:21]

Done.

   InternalInit();
 }
 
@@ -429,7 +428,7 @@ BlinkPlatformImpl::BlinkPlatformImpl(
       shared_timer_fire_time_(0.0),
       shared_timer_fire_time_was_set_while_suspended_(false),
       shared_timer_suspended_(0),
-      current_thread_slot_(&DestroyCurrentThread) {
+      current_thread_slot_() {
   // TODO(alexclarke): Use c++11 delegated constructors when allowed.
   InternalInit();
 }
@@ -452,6 +451,11 @@ void BlinkPlatformImpl::InternalInit() {
   }
 }
 
+void BlinkPlatformImpl::UpdateWebThreadTLS(blink::WebThread* thread) {
+  DCHECK(!current_thread_slot_.Get());
+  current_thread_slot_.Set(thread);
+}
+
 BlinkPlatformImpl::~BlinkPlatformImpl() {
 }
 
@@ -499,23 +503,15 @@ bool BlinkPlatformImpl::isReservedIPAddress(
 }
 
 blink::WebThread* BlinkPlatformImpl::createThread(const char* name) {
-  return new WebThreadImpl(name);
+  WebThreadImpl* thread = new WebThreadImpl(name);
+  thread->TaskRunner()->PostTask(
+      FROM_HERE, base::Bind(&BlinkPlatformImpl::UpdateWebThreadTLS,
+                            base::Unretained(this), thread));
+  return thread;
 }
 
 blink::WebThread* BlinkPlatformImpl::currentThread() {
-  WebThreadImplForMessageLoop* thread =
-      static_cast<WebThreadImplForMessageLoop*>(current_thread_slot_.Get());
-  if (thread)
-    return (thread);
-
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner =
-      MainTaskRunnerForCurrentThread();
-  if (!task_runner.get())
-    return NULL;
-
-  thread = new WebThreadImplForMessageLoop(task_runner);
-  current_thread_slot_.Set(thread);
-  return thread;
+  return static_cast<blink::WebThread*>(current_thread_slot_.Get());
 }
 
 void BlinkPlatformImpl::yieldCurrentThread() {
@@ -1244,13 +1240,6 @@ BlinkPlatformImpl::MainTaskRunnerForCurrentThread() {
   }
 }
 
-// static
-void BlinkPlatformImpl::DestroyCurrentThread(void* thread) {
-  WebThreadImplForMessageLoop* impl =
-      static_cast<WebThreadImplForMessageLoop*>(thread);
-  delete impl;
-}
-
 WebString BlinkPlatformImpl::domCodeStringFromEnum(int dom_code) {
   return WebString::fromUTF8(ui::KeycodeConverter::DomCodeToCodeString(
       static_cast<ui::DomCode>(dom_code)));