Add a v2 closure gyp syntax to Closure wiki

docs/closure_compilation.md

 # Closure Compilation
 
 ## I just need to fix the compile!
 
 To locally run closure compiler like the bots, do this:
 
 ```shell
 cd $CHROMIUM_SRC
 # sudo apt-get install openjdk-7-jre # may be required
-GYP_GENERATORS=ninja tools/gyp/gyp --depth . \
-third_party/closure_compiler/compiled_resources.gyp
+GYP_GENERATORS=ninja tools/gyp/gyp --depth . third_party/closure_compiler/compiled_resources.gyp
 ninja -C out/Default
 ```
 
+To run the v2 gyp format, change the last 2 lines to:
+
+```shell
+# notice the 2 in compiled_resources2.gyp
+GYP_GENERATORS=ninja tools/gyp/gyp --depth . third_party/closure_compiler/compiled_resources2.gyp
+ninja -C out/Default
+```
+
 ## Background
 
 In C++ and Java, compiling the code gives you _some_ level of protection against
 misusing variables based on their type information. JavaScript is loosely typed
 and therefore doesn't offer this safety. This makes writing JavaScript more
 error prone as it's _one more thing_ to mess up.
 
 Because having this safety is handy, Chrome now has a way to optionally
 typecheck your JavaScript and produce compiled output with
 [Closure Compiler](https://developers.google.com/closure/compiler/).
@@ skipping 247 matching lines @@
           'jscomp_error=duplicate',
           'jscomp_error=misplacedTypeAnnotation',
         ],
         'disabled_closure_args': [], # remove the disabled closure args for more strict compilation
       },
       'includes': ['../third_party/closure_compiler/compile_js.gypi'],
     },
   ],
 }
 ```