Remove calls to MessageLoop::current() in tools.

tools/gn/loader.cc

Index: tools/gn/loader.cc
diff --git a/tools/gn/loader.cc b/tools/gn/loader.cc
index 69fb7668e17dd200c23ec5b37a7f591c5f774d5a..54e36495f50f7966954affd5cdef1745e2a7d3a1 100644
--- a/tools/gn/loader.cc
+++ b/tools/gn/loader.cc
@@ -6,8 +6,7 @@
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
-#include "base/message_loop/message_loop.h"
-#include "base/single_thread_task_runner.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "tools/gn/build_settings.h"
 #include "tools/gn/err.h"
 #include "tools/gn/filesystem_utils.h"
@@ -100,9 +99,9 @@ SourceFile Loader::BuildFileForLabel(const Label& label) {
 // -----------------------------------------------------------------------------
 
 LoaderImpl::LoaderImpl(const BuildSettings* build_settings)
-    : main_loop_(base::MessageLoop::current()),
-      pending_loads_(0),
-      build_settings_(build_settings) {
+    : pending_loads_(0), build_settings_(build_settings) {
+  if (base::ThreadTaskRunnerHandle::IsSet())

[brettw, 2016/07/11 20:47:25]

Can you add a comment here that there may be no active task runner set at this
point, in which case we expect the calling code to call set_task_runner(). It
initially looked weird that you handled the unset case.

[fdoray, 2016/07/18 15:28:40]

Done.

+    task_runner_ = base::ThreadTaskRunnerHandle::Get();
 }
 
 LoaderImpl::~LoaderImpl() {
@@ -239,7 +238,7 @@ void LoaderImpl::BackgroundLoadFile(const Settings* settings,
                                     const LocationRange& origin,
                                     const ParseNode* root) {
   if (!root) {
-    main_loop_->task_runner()->PostTask(
+    task_runner_->PostTask(
         FROM_HERE, base::Bind(&LoaderImpl::DecrementPendingLoads, this));
     return;
   }
@@ -280,8 +279,7 @@ void LoaderImpl::BackgroundLoadFile(const Settings* settings,
 
   trace.Done();
 
-  main_loop_->task_runner()->PostTask(
-      FROM_HERE, base::Bind(&LoaderImpl::DidLoadFile, this));
+  task_runner_->PostTask(FROM_HERE, base::Bind(&LoaderImpl::DidLoadFile, this));
 }
 
 void LoaderImpl::BackgroundLoadBuildConfig(
@@ -289,7 +287,7 @@ void LoaderImpl::BackgroundLoadBuildConfig(
     const Scope::KeyValueMap& toolchain_overrides,
     const ParseNode* root) {
   if (!root) {
-    main_loop_->task_runner()->PostTask(
+    task_runner_->PostTask(
         FROM_HERE, base::Bind(&LoaderImpl::DecrementPendingLoads, this));
     return;
   }
@@ -339,9 +337,9 @@ void LoaderImpl::BackgroundLoadBuildConfig(
     }
   }
 
-  main_loop_->task_runner()->PostTask(
-      FROM_HERE, base::Bind(&LoaderImpl::DidLoadBuildConfig, this,
-                            settings->toolchain_label()));
+  task_runner_->PostTask(FROM_HERE,
+                         base::Bind(&LoaderImpl::DidLoadBuildConfig, this,
+                                    settings->toolchain_label()));
 }
 
 void LoaderImpl::DidLoadFile() {