Disable Clang's warnings about undefined pointer comparisons in Debug builds

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index b2bf16bc44081fa937744aba5cc44f03059ec0a7..be5f50984381917adacf79a5f528798bfc0ec910 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -3231,6 +3231,30 @@
               ],
             },
           }],
+          ['clang==1', {
+            'cflags': [
+              # Allow comparing the address of references and 'this' against 0
+              # in debug builds. Technically, these can never be null in
+              # well-defined C/C++ and Clang can optimize such checks away in
+              # release builds, but they may be used in asserts in debug builds.
+              '-Wno-undefined-bool-conversion',
+              '-Wno-tautological-undefined-compare',
+            ],
+            'xcode_settings': {
+              'OTHER_CFLAGS': [
+                '-Wno-undefined-bool-conversion',
+                '-Wno-tautological-undefined-compare',
+              ],
+            },
+            'msvs_settings': {
+              'VCCLCompilerTool': {
+                'AdditionalOptions': [
+                  '-Wno-undefined-bool-conversion',
+                  '-Wno-tautological-undefined-compare',
+                ],
+              },
+            },
+          }],
         ],
       },
       'Release_Base': {