Add a gyp flag to allow removing dependency on ppapi.

chrome/browser/chrome_content_browser_client.cc

Index: chrome/browser/chrome_content_browser_client.cc
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index cd5048a8ea4eb4818d9fdd23d217ff365a616363..0189c1345180845cdb339ab2609ffd4164a37d80 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -625,7 +625,9 @@ void ChromeContentBrowserClient::RenderProcessHostCreated(
 
 void ChromeContentBrowserClient::BrowserChildProcessHostCreated(
     content::BrowserChildProcessHost* host) {
+#if defined(ENABLE_PPAPI)
   host->GetHost()->AddFilter(new PepperGtalkMessageFilter());
+#endif
 }
 
 content::WebUIControllerFactory*
@@ -1756,9 +1758,11 @@ std::string ChromeContentBrowserClient::GetDefaultDownloadName() {
 
 void ChromeContentBrowserClient::DidCreatePpapiPlugin(
     content::BrowserPpapiHost* browser_host) {
+#if defined(ENABLE_PPAPI)
   browser_host->GetPpapiHost()->AddHostFactoryFilter(
       scoped_ptr<ppapi::host::HostFactory>(
           new ChromeBrowserPepperHostFactory(browser_host)));
+#endif
 }
 
 content::BrowserPpapiHost*