Add a gyp flag to allow removing dependency on ppapi.

content/content_browser.gypi

Index: content/content_browser.gypi
diff --git a/content/content_browser.gypi b/content/content_browser.gypi
index f35d9f17f64ea20a06ef284fdaee7068a73b5688..f3f6f460be0b52489b80e159991dc999733e8248 100644
--- a/content/content_browser.gypi
+++ b/content/content_browser.gypi
@@ -929,7 +929,6 @@
         'browser/debugger/devtools_resources.gyp:devtools_resources',
         '../cc/cc.gyp:cc',
         '../net/net.gyp:http_server',
-        '../ppapi/ppapi_internal.gyp:ppapi_ipc',
         '../printing/printing.gyp:printing',
         '<(webkit_src_dir)/Source/WebKit/chromium/WebKit.gyp:webkit',
         '../ui/surface/surface.gyp:surface',
@@ -1122,6 +1121,18 @@
         ['exclude', '^browser/renderer_host/tap_suppression_controller_aura.cc'],
       ],
     }],
+    ['enable_ppapi==1', {
+      'dependencies': [
+        '../ppapi/ppapi_internal.gyp:ppapi_ipc',
+      ],
+    }, {  # enable_ppapi==0
+      'sources!': [
+        'browser/ppapi_plugin_process_host.cc',
+      ],
+      'sources/': [
+        ['exclude', '^browser/renderer_host/pepper/'],
+      ],
+    }],
     ['java_bridge==1', {
       'defines': [
         'ENABLE_JAVA_BRIDGE',