Add a gyp flag to allow removing dependency on ppapi.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 7388b7e458ac3c498f5af8061a1bc884da2c6ad5..c7ee94a78278588d33a65bcb74e7e29ada84e77e 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -376,6 +376,11 @@
       # Enable plug-in installation by default.
       'enable_plugin_installation%': 1,
 
+      # Enable PPAPI and NPAPI by default.
+      # TODO(nileshagrawal): Make this flag enable/disable NPAPI as well
+      # as PPAPI; see crbug.com/162667.
+      'enable_plugins%': 1,
+
       # Enable protector service by default.
       'enable_protector_service%': 1,
 
@@ -527,6 +532,12 @@
         }],
 
         ['OS=="android" or OS=="ios"', {
+          'enable_plugins%': 0,
+        }, {
+          'enable_plugins%': 1,
+        }],
+
+        ['OS=="android" or OS=="ios"', {
           'enable_protector_service%': 0,
         }, {
           'enable_protector_service%': 1,
@@ -669,6 +680,7 @@
     'enable_web_intents%': '<(enable_web_intents)',
     'enable_web_intents_tag%': '<(enable_web_intents_tag)',
     'enable_plugin_installation%': '<(enable_plugin_installation)',
+    'enable_plugins%': '<(enable_plugins)',
     'enable_protector_service%': '<(enable_protector_service)',
     'enable_session_service%': '<(enable_session_service)',
     'enable_themes%': '<(enable_themes)',
@@ -1861,6 +1873,9 @@
       ['enable_plugin_installation==1', {
         'defines': ['ENABLE_PLUGIN_INSTALLATION=1'],
       }],
+      ['enable_plugins==1', {
+        'defines': ['ENABLE_PLUGINS=1'],
+      }],
       ['enable_protector_service==1', {
         'defines': ['ENABLE_PROTECTOR_SERVICE=1'],
       }],