Fix typo at endif in InspectorHelperMixin class

TBR=rtoy

Bug: 972733
Change-Id: Iee1148c9d9172378cdf6120a1b2461c1d100e679
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1693907Reviewed-by: Raymond Toy <rtoy@chromium.org>
Commit-Queue: Hongchan Choi <hongchan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#676089}

third_party/blink/renderer/modules/webaudio/inspector_helper_mixin.h

@@ -30,4 +30,4 @@ class InspectorHelperMixin {
 
 }  // namespace blink
 
-#endif  // THIRD_PARTY_BLINK_RENDERER_MODULES_WEBAUDIO_INSPECTOR_HELPER_H_
+#endif  // THIRD_PARTY_BLINK_RENDERER_MODULES_WEBAUDIO_INSPECTOR_HELPER_MIXIN_H_