--- a/dom/media/platforms/omx/moz.build
+++ b/dom/media/platforms/omx/moz.build
@@ -43,8 +43,15 @@ if CONFIG['MOZ_WIDGET_TOOLKIT'] == 'gonk
     EXTRA_DSO_LDOPTS += [
         '-libbinder',
     ]
 
 FINAL_LIBRARY = 'xul'
 
 if CONFIG['GNU_CXX']:
     CXXFLAGS += ['-Wno-error=shadow']
+
+if CONFIG['_MSC_VER']:
+    # Avoid warnings from third-party code that we can not modify.
+    if CONFIG['CLANG_CL']:
+        CXXFLAGS += ['-Wno-invalid-source-encoding']
+    else:
+        CXXFLAGS += ['-validate-charset-']

--- a/media/webrtc/moz.build
+++ b/media/webrtc/moz.build
@@ -89,16 +89,23 @@ if CONFIG['MOZ_WEBRTC_SIGNALING']:
         'signaling/src/sdp/sipcc/sdp_services_unix.c',
         'signaling/src/sdp/sipcc/sdp_token.c',
         'signaling/src/sdp/sipcc/sdp_utils.c',
     ]
 
     GYP_DIRS['signaling'].sandbox_vars['ALLOW_COMPILER_WARNINGS'] = True
     GYP_DIRS['signaling'].non_unified_sources += signaling_non_unified_sources
 
+    if CONFIG['_MSC_VER']:
+        # Avoid warnings from third-party code that we can not modify.
+        if CONFIG['CLANG_CL']:
+            CXXFLAGS += ['-Wno-invalid-source-encoding']
+        else:
+            CXXFLAGS += ['-validate-charset-']
+
 if CONFIG['MOZ_WIDGET_TOOLKIT'] != 'gonk':
     GYP_DIRS += ['trunk/testing']
     GYP_DIRS['trunk/testing'].input = 'trunk/testing/gtest.gyp'
     GYP_DIRS['trunk/testing'].variables = gyp_vars
     # We allow warnings for third-party code that can be updated from upstream.
     GYP_DIRS['trunk/testing'].sandbox_vars['ALLOW_COMPILER_WARNINGS'] = True
     GYP_DIRS['trunk/testing'].non_unified_sources += webrtc_non_unified_sources