Change the test_isolation_outdir default from PRODUCT_DIR to PRODUCT_DIR/isolate

Otherwise a lot of spew is generated when using test_isolation_mode=hashtable.
Do not use hashtable since outdir is also used with _run and _remap.

R=mad@chromium.org
BUG=98636
TEST=

Review URL: https://chromiumcodereview.appspot.com/10382238

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@137914 0039d316-1c4b-4281-b951-d872f2087c98

build/common.gypi

@@ -352,7 +352,7 @@
       'test_isolation_mode%': 'noop',
       # It must not be '<(PRODUCT_DIR)' alone, the '/' is necessary otherwise
       # gyp will remove duplicate flags, causing isolate.py to be confused.
-      'test_isolation_outdir%': '<(PRODUCT_DIR)/',
+      'test_isolation_outdir%': '<(PRODUCT_DIR)/isolate',
 
        # Force rlz to use chrome's networking stack.
       'force_rlz_use_chrome_net%': 1,