Add an UMA metric to track whether chrome is running on a tablet.

base/base.gyp

Index: base/base.gyp
diff --git a/base/base.gyp b/base/base.gyp
index 06ad10bfb3c002c8cf60ad42641111d3a104120a..e9c3aea397e9a5bc5fda4c3434d6cc116cd22f92 100644
--- a/base/base.gyp
+++ b/base/base.gyp
@@ -183,6 +183,18 @@
             ],
           },
         }],
+        ['OS == "win"', {
+          'msvs_settings': {
+            'VCLinkerTool': {
+              'DelayLoadDLLs': [
+                'powrprof.dll',
+              ],
+              'AdditionalDependencies': [
+                'powrprof.lib',
+              ],
+            },
+          },
+        }],
         ['OS != "win" and OS != "ios"', {
             'dependencies': ['../third_party/libevent/libevent.gyp:libevent'],
         },],