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 LayoutTestContentBrowserClient::RenderProcessWillLaunch(
    RenderProcessHost* host) {
  ShellContentBrowserClient::RenderProcessWillLaunch(host);

  StoragePartition* partition =
      BrowserContext::GetDefaultStoragePartition(browser_context());
  host->AddFilter(new LayoutTestMessageFilter(
      host->GetID(),
      partition->GetDatabaseTracker(),
      partition->GetQuotaManager(),
      partition->GetURLRequestContext()));

  host->Send(new ShellViewMsg_SetWebKitSourceDir(GetWebKitRootDirFilePath()));
}

void LayoutTestContentBrowserClient::RenderProcessWillLaunch(
    RenderProcessHost* host) {
  ShellContentBrowserClient::RenderProcessWillLaunch(host);

  StoragePartition* partition =
      BrowserContext::GetDefaultStoragePartition(browser_context());
  host->AddFilter(new LayoutTestMessageFilter(
      host->GetID(),
      partition->GetDatabaseTracker(),
      partition->GetQuotaManager(),
      partition->GetURLRequestContext()));

  host->Send(new ShellViewMsg_SetWebKitSourceDir(GetWebKitRootDirFilePath()));
}
