Blimp: relocate thread-unsafe member getter in DropConnection code.

There is logic in the ClientSession/ClientContext which attempts
to drop a connection on the IO thread. Unfortunately, in doing so,
it called a thread-unsafe member getter within the call to PostTask.

This CL moves the getter into a helper method which runs entirely
on the IO thread.

R=nyquist@chromium.org,wez@chromium.org
CC=steimel@chromium.org
BUG=647814

Review-Url: https://codereview.chromium.org/2344893009
Cr-Commit-Position: refs/heads/master@{#419491}

blimp/client/core/blimp_client_context_impl.cc

@@ -38,8 +38,14 @@ namespace blimp {
 namespace client {
 
 namespace {
+
 const char kDefaultAssignerUrl[] =
     "https://blimp-pa.googleapis.com/v1/assignment";
+
+void DropConnectionOnIOThread(ClientNetworkComponents* net_components) {
+  net_components->GetBrowserConnectionHandler()->DropCurrentConnection();
+}
+
 }  // namespace
 
 // This function is declared in //blimp/client/public/blimp_client_context.h,
@@ -226,6 +232,11 @@ void BlimpClientContextImpl::InitializeSettings() {
     settings_feature_->SetRecordWholeDocument(true);
 }
 
+void BlimpClientContextImpl::DropConnection() {
+  io_thread_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&DropConnectionOnIOThread, net_components_.get()));
+}
+
 void BlimpClientContextImpl::CreateIdentitySource() {
   identity_source_ = base::MakeUnique<IdentitySource>(
       delegate_, base::Bind(&BlimpClientContextImpl::OnAuthTokenReceived,
@@ -234,11 +245,7 @@ void BlimpClientContextImpl::CreateIdentitySource() {
 
 void BlimpClientContextImpl::OnImageDecodeError() {
   // Currently we just drop the connection on image decoding error.
-  io_thread_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(
-          &BrowserConnectionHandler::DropCurrentConnection,
-          base::Unretained(net_components_->GetBrowserConnectionHandler())));
+  DropConnection();
 }
 
 }  // namespace client

blimp/client/core/blimp_client_context_impl.h

@@ -84,6 +84,10 @@ class BlimpClientContextImpl
   void RegisterFeatures();
   void InitializeSettings();
 
+  // Terminates the active connection held by |net_connections_|.
+  // May be called on any thread.
+  void DropConnection();
+
   // Create IdentitySource which provides user sign in states and OAuth2 token
   // service.
   void CreateIdentitySource();

blimp/client/session/blimp_client_session.cc

@@ -13,6 +13,7 @@
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/sequenced_task_runner.h"
+#include "base/task_runner_util.h"
 #include "base/threading/sequenced_task_runner_handle.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ -37,6 +38,13 @@
 
 namespace blimp {
 namespace client {
+namespace {
+
+void DropConnectionOnIOThread(ClientNetworkComponents* net_components) {
+  net_components->GetBrowserConnectionHandler()->DropCurrentConnection();
+}
+
+}  // namespace
 
 BlimpClientSession::BlimpClientSession(const GURL& assigner_endpoint)
     : io_thread_("BlimpIOThread"),
@@ -149,16 +157,17 @@ void BlimpClientSession::RegisterFeatures() {
     settings_feature_->SetRecordWholeDocument(true);
 }
 
+void BlimpClientSession::DropConnection() {
+  io_thread_.task_runner()->PostTask(
+      FROM_HERE, base::Bind(&DropConnectionOnIOThread, net_components_.get()));
+}
+
 void BlimpClientSession::OnConnected() {}
 
 void BlimpClientSession::OnDisconnected(int result) {}
 
 void BlimpClientSession::OnImageDecodeError() {
-  io_thread_.task_runner()->PostTask(
-      FROM_HERE,
-      base::Bind(
-          &BrowserConnectionHandler::DropCurrentConnection,
-          base::Unretained(net_components_->GetBrowserConnectionHandler())));
+  DropConnection();
 }
 
 TabControlFeature* BlimpClientSession::GetTabControlFeature() const {

blimp/client/session/blimp_client_session.h

@@ -86,6 +86,10 @@ class BlimpClientSession
  private:
   void RegisterFeatures();
 
+  // Terminates the active connection held by |net_connections_| on the IO
+  // thread. Should be called on the main thread.
+  void DropConnection();
+
   // NetworkEventObserver implementation.
   void OnConnected() override;
   void OnDisconnected(int result) override;