Update build utils to prefer Visual Studio 2013.

BUG=
R=ricow@google.com

Review URL: https://codereview.chromium.org//1257013004 .

tools/utils.py

diff --git a/tools/utils.py b/tools/utils.py
index ec6312e..262a4ad 100644
--- a/tools/utils.py
+++ b/tools/utils.py
@@ -97,7 +97,7 @@
 
 # Try to guess Visual Studio location when buiding on Windows.
 def GuessVisualStudioPath():
-  defaultPath = r"C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7" \
+  defaultPath = r"C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7" \
                 r"\IDE"
   defaultExecutable = "devenv.com"
 
@@ -142,8 +142,8 @@
               # Can't find value under the key - continue to the next key.
               continue
             isExpress = executable != 'devenv.com'
-            if not isExpress and subkeyName == '10.0':
-              # Stop search since if we found non-Express VS2010 version
+            if not isExpress and subkeyName == '12.0':
+              # Stop search since if we found non-Express VS2013 version
               # installed, which is preferred version.
               return installDir, executable
             else: