DevTools: move DevToolsAgent/Client into content.

BUG=84078
TEST=

Review URL: http://codereview.chromium.org/7461019

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@93596 0039d316-1c4b-4281-b951-d872f2087c98
  virtual net::URLRequestContext* GetRequestContext(
      ResourceType::Type resource_type) {
    net::URLRequestContextGetter* request_context = request_context_;
    if (resource_type == ResourceType::MEDIA)
      request_context = media_request_context_;
    return request_context->GetURLRequestContext();
  }

  virtual net::URLRequestContext* GetRequestContext(
      ResourceType::Type resource_type) {
    net::URLRequestContextGetter* request_context = request_context_;
    if (resource_type == ResourceType::MEDIA)
      request_context = media_request_context_;
    return request_context->GetURLRequestContext();
  }
