Don't build sync_unit_tests for the Dr.Memory runs

We don't run sync_unit_tests now and it's so big and slow it affects both the
performance and the stability of building.
For example, it doesn't build on the Dr.Memory trybot now.

TBR=bruening
Review URL: http://codereview.chromium.org/8816015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@113187 0039d316-1c4b-4281-b951-d872f2087c98

build/all.gyp

@@ -508,7 +508,6 @@
           'type': 'none',
           'dependencies': [
             '../base/base.gyp:base_unittests',
-            '../chrome/chrome.gyp:sync_unit_tests',
             '../chrome/chrome.gyp:unit_tests',
             '../content/content.gyp:content_unittests',
             '../crypto/crypto.gyp:crypto_unittests',