[test] Apply more detailed origin tracking in MSAN builds.

BUG=chromium:425187
LOG=n
TBR=svenpanne@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/1148333004

Cr-Commit-Position: refs/heads/master@{#28561}

build/standalone.gypi

@@ -38,7 +38,7 @@
     # Track where uninitialized memory originates from. From fastest to
     # slowest: 0 - no tracking, 1 - track only the initial allocation site, 2
     # - track the chain of stores leading from allocation site to use site.
-    'msan_track_origins%': 1,
+    'msan_track_origins%': 2,
     'visibility%': 'hidden',
     'v8_enable_backtrace%': 0,
     'v8_enable_i18n_support%': 1,