Make ChromeOS imply enable_hidpi

Bug=None
Test=Compile ChromeOS without enable_hidpi GYP_DEFINE.

R=flackr
TBR=sky

Review URL: https://chromiumcodereview.appspot.com/10829281

git-svn-id: http://src.chromium.org/svn/trunk/src/build@151160 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -125,8 +125,8 @@
             'toolkit_uses_gtk%': 0,
           }],
 
-          # Enable HiDPI on Mac OS.
-          ['OS=="mac"', {
+          # Enable HiDPI on Mac OS and Chrome OS.
+          ['OS=="mac" or chromeos==1', {
             'enable_hidpi%': 1,
           }],