Revert 153092 - Turn on warnings as errors for (most) third_party code on Windows

Is causing warnings for Official build in PDF code. Boo.

-----------------

Can't quite be fully enabled yet due to not-yet-fixed third party
dependencies. Without it enabled, other packages regress while we're fixing
things. So, add a flag for now so warnings-freeness can be ratcheted forward
by having it on for most packages, but off for a few.

Also, disable warning in qcms (fixed upstream by a large refactoring, not
worth rolling for), and disable two minor warnings in yasm (patch posted
upstream for a few months, but maintainer does not seem motivated to merge).

Fix release-only warning in leveldatabase/env_chromium.cc. Was calling exit(1)
in a leaky destructor.

Fix a warning in lzma_sdk (missing an include).

Disable a silly warning in Release builds of skia and memory_watcher (that
/GS is not working because optimization is disabled).

Warning are currently tolerated in libvpx and mesa.

Cannot be committed until http://chromiumcodereview.appspot.com/10823426/ has
landed.

R=thakis@chromium.org
BUG=126483,140121, 143877
TEST=


Review URL: https://chromiumcodereview.appspot.com/10827429

TBR=scottmg@chromium.org
Review URL: https://chromiumcodereview.appspot.com/10872063

git-svn-id: http://src.chromium.org/svn/trunk/src/build@153223 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -710,14 +710,6 @@
     # to get incremental linking to be faster in debug builds.
     'incremental_chrome_dll%': '0',
 
-    # The default settings for third party code for treating
-    # warnings-as-errors. Ideally, this would not be required, however there
-    # is some third party code that takes a long time to fix/roll. So, this
-    # flag allows us to have warnings as errors in general to prevent
-    # regressions in most modules, while working on the bits that are
-    # remaining.
-    'win_third_party_warn_as_error%': 'true',
-
     # This is the location of the sandbox binary. Chrome looks for this before
     # running the zygote process. If found, and SUID, it will be used to
     # sandbox the zygote process and, thus, all renderer processes.
@@ -1685,7 +1677,7 @@
             'msvs_settings': {
               'VCCLCompilerTool': {
                 'WarningLevel': '3',
-                'WarnAsError': '<(win_third_party_warn_as_error)',
+                'WarnAsError': 'false', # TODO(maruel): Enable it.
                 'Detect64BitPortabilityProblems': 'false',
               },
             },