Yesterday several builds failed with GOMA_BUILD_ERROR in the compile step. 

Many of the errors in the logs look like this:

[281/7246] CXX obj/skia/skia/SkPDFDevice.obj
FAILED: obj/skia/skia/SkPDFDevice.obj 
ninja -t msvc -e environment.x64 -- E:\b\c\cipd\goma/gomacc.exe "E:\b\depot_tools\win_toolchain\vs_files\d5dc33b15d1b2c086f2f6632e2fd15882f80dbd3\VC\bin\amd64/cl.exe" /nologo /showIncludes /FC @obj/skia/skia/SkPDFDevice.obj.rsp /c ../../third_party/skia/src/pdf/SkPDFDevice.cpp /Foobj/skia/skia/SkPDFDevice.obj /Fd"obj/skia/skia_cc.pdb"
GOMA:cl.exe ../../third_party/skia/src/pdf/SkPDFDevice.cpp:*ERROR*: compiler_proxy:66ms: reached max number of active fail fallbacks

I don't understand what is happening here. Assigning to ukai to take a look. Was this an issue with Goma? Some examples linked below.

Logs:
https://luci-logdog.appspot.com/v/?s=chromium/bb/tryserver.chromium.win/win_chromium_x64_rel_ng/312783/+/recipes/steps/compile__with_patch_/0/stdout
https://luci-logdog.appspot.com/v/?s=chromium/bb/tryserver.chromium.win/win_chromium_x64_rel_ng/312750/+/recipes/steps/compile__with_patch_/0/stdout
https://luci-logdog.appspot.com/v/?s=chromium/bb/tryserver.chromium.win/win_chromium_rel_ng/327186/+/recipes/steps/compile__with_patch_/0/stdout
https://luci-logdog.appspot.com/v/?s=chromium/bb/tryserver.chromium.win/win_chromium_rel_ng/327225/+/recipes/steps/compile__with_patch_/0/stdout
https://luci-logdog.appspot.com/v/?s=chromium/bb/tryserver.chromium.android/android_n5x_swarming_rel/63220/+/recipes/steps/compile__with_patch_/0/stdout
https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Ftryserver.chromium.android%2Fandroid_n5x_swarming_rel%2F63238%2F%2B%2Frecipes%2Fsteps%2Fcompile__with_patch_%2F0%2Fstdout

Builds:
https://luci-milo.appspot.com/buildbot/tryserver.chromium.win/win_chromium_x64_rel_ng/312750
https://luci-milo.appspot.com/buildbot/tryserver.chromium.win/win_chromium_x64_rel_ng/312783
https://luci-milo.appspot.com/buildbot/tryserver.chromium.win/win_chromium_rel_ng/327186
https://luci-milo.appspot.com/buildbot/tryserver.chromium.win/win_chromium_rel_ng/327225
https://build.chromium.org/p/tryserver.chromium.android/builders/android_n5x_swarming_rel/builds/63220
https://build.chromium.org/p/tryserver.chromium.android/builders/android_n5x_swarming_rel/builds/63238