improve layout tests by removing definition of DEBUG (libxml uses it to spew diagnostic output to stderr)

Review URL: http://codereview.chromium.org/7149

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@3394 0039d316-1c4b-4281-b951-d872f2087c98

build/debug.xcconfig

@@ -6,7 +6,10 @@
 
 COPY_PHASE_STRIP = NO
 GCC_OPTIMIZATION_LEVEL = 0
-GCC_PREPROCESSOR_DEFINITIONS = $(GCC_PREPROCESSOR_DEFINITIONS) DEBUG
+// Would be nice to define DEBUG to prevent against people incorrectly using
+// it intstead of !NDEBUG, but it causes libxml to spew diagnostic info all
+// over our layout tests.
+// GCC_PREPROCESSOR_DEFINITIONS = $(GCC_PREPROCESSOR_DEFINITIONS) DEBUG
 // Additional libc++ strictness; disabled because they break some things in
 // WebKit and some additional things when building with gcc 4.2.
 // GCC_PREPROCESSOR_DEFINITIONS = $(GCC_PREPROCESSOR_DEFINITIONS) DEBUG _GLIBCXX_CONCEPT_CHECKS _GLIBCXX_DEBUG _GLIBCXX_DEBUG_PEDANTIC