Add format tag info to CoreAudioUtil::GetSharedModeMixFormat DCHECK.

Will help understand why the DCHECK is hit.

Bug: 803056
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Ibd00659e0ae1024cb863d90cd4e32e3f3f542a7c
Reviewed-on: https://chromium-review.googlesource.com/893318Reviewed-by: Max Morin <maxmorin@chromium.org>
Commit-Queue: Henrik Grunell <grunell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532868}

media/audio/win/core_audio_util_win.cc

@@ -672,7 +672,8 @@ HRESULT CoreAudioUtil::GetSharedModeMixFormat(
     return hr;
 
   size_t bytes = sizeof(WAVEFORMATEX) + format_pcmex->Format.cbSize;
-  DCHECK_EQ(bytes, sizeof(WAVEFORMATPCMEX));
+  DCHECK_EQ(bytes, sizeof(WAVEFORMATPCMEX))
+      << "Format tag: 0x" << std::hex << format_pcmex->Format.wFormatTag;
 
   memcpy(format, format_pcmex, bytes);
   DVLOG(2) << *format;