Enable some more MSVS compiler warnings.

build/common_defines.gypi

@@ -11,7 +11,19 @@
         'angle_build_winrt%': '0',
         'angle_build_winphone%': '0',
     },
-    'msvs_disabled_warnings': [ 4075, 4100, 4127, 4239, 4244, 4245, 4251, 4264, 4267, 4447, 4702, 4718 ],
+    'msvs_disabled_warnings':
+    [
+        4100, # Unreferenced formal parameter. Not interesting.
+        4127, # conditional expression is constant. Too noisy to be useful.
+
+        # Conversion warnings.  These fire all over the place in ANGLE.
+        4244, # Conversion from 'type1' to 'type2', possible loss of data
+        4245, # Conversion from 'type1' to 'type2', signed/unsigned mismatch
+        4267, # Conversion from 'size_t' to 'type', possible loss of data
+
+        4702, # Unreachable code. Useful, but fires on system header xtree.
+        4718, # Recursive call has no side effects. Fires on xtree too.
+    ],
     'msvs_system_include_dirs':
     [
         '<(windows_sdk_path)/Include/shared',