content: Rename webkit_test_helpers.{cc,h} to blink_test_helpers.{cc,h}

Now that webkit/ is gone, we are preparing ourselves for the merge of
third_party/WebKit into //blink.

BUG=None
BUG=content_shell && content_unittests
R=avi@chromium.org

Review URL: https://codereview.chromium.org/1118183003

Cr-Commit-Position: refs/heads/master@{#328202}
void WebKitTestController::OnResetDone() {
  if (is_leak_detection_enabled_) {
    if (main_window_ && main_window_->web_contents()) {
      RenderViewHost* render_view_host =
          main_window_->web_contents()->GetRenderViewHost();
      render_view_host->Send(
          new ShellViewMsg_TryLeakDetection(render_view_host->GetRoutingID()));
    }
    return;
  }

  base::MessageLoop::current()->PostTask(FROM_HERE,
                                         base::MessageLoop::QuitClosure());
}

void WebKitTestController::OnResetDone() {
  if (is_leak_detection_enabled_) {
    if (main_window_ && main_window_->web_contents()) {
      RenderViewHost* render_view_host =
          main_window_->web_contents()->GetRenderViewHost();
      render_view_host->Send(
          new ShellViewMsg_TryLeakDetection(render_view_host->GetRoutingID()));
    }
    return;
  }

  base::MessageLoop::current()->PostTask(FROM_HERE,
                                         base::MessageLoop::QuitClosure());
}
