Add a gyp flag to allow removing dependency on ppapi.

chrome/chrome_renderer.gypi

Index: chrome/chrome_renderer.gypi
diff --git a/chrome/chrome_renderer.gypi b/chrome/chrome_renderer.gypi
index ad02ddeac68ac9294b8862abc13fe254ca18dd75..9310f23ca8d8eb15298d1381b3c0f8fcab98e421 100644
--- a/chrome/chrome_renderer.gypi
+++ b/chrome/chrome_renderer.gypi
@@ -15,10 +15,6 @@
         'chrome_resources.gyp:chrome_strings',
         '../content/content.gyp:content_renderer',
         '../net/net.gyp:net',
-        '../ppapi/ppapi_internal.gyp:ppapi_host',
-        '../ppapi/ppapi_internal.gyp:ppapi_proxy',
-        '../ppapi/ppapi_internal.gyp:ppapi_ipc',
-        '../ppapi/ppapi_internal.gyp:ppapi_shared',
         '../printing/printing.gyp:printing',
         '../skia/skia.gyp:skia',
         '../third_party/hunspell/hunspell.gyp:hunspell',
@@ -288,6 +284,18 @@
             'nacl',
           ],
         }],
+        ['enable_ppapi==1', {
+          'dependencies': [
+            '../ppapi/ppapi_internal.gyp:ppapi_host',
+            '../ppapi/ppapi_internal.gyp:ppapi_proxy',
+            '../ppapi/ppapi_internal.gyp:ppapi_ipc',
+            '../ppapi/ppapi_internal.gyp:ppapi_shared',
+          ],
+        }, {  # enable_ppapi==0
+          'sources/': [
+            ['exclude', '^renderer/pepper/'],
+          ],
+        }],
         ['safe_browsing==1', {
           'defines': [
             'FULL_SAFE_BROWSING',