I have been working on incrementally allowing clang plugin warnings to be enabled in Blink, but this seems to have introduced a regression in the plugin. See https://chromium-review.googlesource.com/c/chromium/src/+/750268

Build config:
Writing """\
goma_dir = "/b/c/goma_client"
is_chrome_branded = true
is_debug = false
is_official_build = true
strip_absolute_paths_from_debug_symbols = true
target_os = "chromeos"
use_goma = true
""" to /b/c/b/Google_Chrome_ChromeOS/src/out/Release/args.gn.

Failed command:
FAILED: obj/third_party/WebKit/Source/core/page/page/PageWidgetDelegate.o 
/b/c/goma_client/gomacc ../../third_party/llvm-build/Release+Asserts/bin/clang++ -MMD -MF obj/third_party/WebKit/Source/core/page/page/PageWidgetDelegate.o.d -DV8_DEPRECATION_WARNINGS -DUSE_UDEV -DUSE_AURA=1 -DUSE_NSS_CERTS=1 -DUSE_OZONE=1 -DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL -DOFFICIAL_BUILD -DGOOGLE_CHROME_BUILD -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -DNO_UNWIND_TABLES -DCR_CLANG_REVISION=\"315613-2\" -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D_FORTIFY_SOURCE=2 -DOS_CHROMEOS -D_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS -D_LIBCXXABI_DISABLE_VISIBILITY_ANNOTATIONS -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -DBLINK_CORE_IMPLEMENTATION=1 -DGL_GLEXT_PROTOTYPES -DUSE_GLX -DUSE_EGL -DBLINK_IMPLEMENTATION=1 -DINSIDE_BLINK -DU_USING_ICU_NAMESPACE=0 -DU_ENABLE_DYLOAD=0 -DU_STATIC_IMPLEMENTATION -DICU_UTIL_DATA_IMPL=ICU_UTIL_DATA_FILE -DUCHAR_TYPE=uint16_t -DGOOGLE_PROTOBUF_NO_RTTI -DGOOGLE_PROTOBUF_NO_STATIC_INITIALIZER -DHAVE_PTHREAD -DSK_IGNORE_LINEONLY_AA_CONVEX_PATH_OPTS -DSK_HAS_PNG_LIBRARY -DSK_HAS_WEBP_LIBRARY -DSK_HAS_JPEG_LIBRARY -DSK_SUPPORT_GPU=1 -DWTF_USE_WEBAUDIO_FFMPEG=1 -DWTF_USE_DEFAULT_RENDER_THEME=1 -DUSE_LIBJPEG_TURBO=1 -DLIBXSLT_STATIC -I../.. -Igen -I../../third_party/WebKit/Source -I../../third_party/WebKit -Igen/blink -Igen/third_party/WebKit -I../../third_party/khronos -I../../gpu -I../../third_party/libwebp/src -I../../third_party/WebKit/Source -Igen/blink -I../../third_party/ced/src -I../../third_party/icu/source/common -I../../third_party/icu/source/i18n -I../../third_party/protobuf/src -I../../skia/config -I../../skia/ext -I../../third_party/skia/include/c -I../../third_party/skia/include/config -I../../third_party/skia/include/core -I../../third_party/skia/include/effects -I../../third_party/skia/include/encode -I../../third_party/skia/include/gpu -I../../third_party/skia/include/images -I../../third_party/skia/include/lazy -I../../third_party/skia/include/pathops -I../../third_party/skia/include/pdf -I../../third_party/skia/include/pipe -I../../third_party/skia/include/ports -I../../third_party/skia/include/utils -I../../third_party/skia/third_party/vulkan -I../../third_party/skia/src/gpu -I../../third_party/skia/src/sksl -I../../third_party/libwebm/source -I../../third_party/protobuf/src -Igen/protoc_out -I../../third_party/boringssl/src/include -I../../build/linux/debian_jessie_amd64-sysroot/usr/include/nss -I../../build/linux/debian_jessie_amd64-sysroot/usr/include/nspr -I../../third_party/libjpeg_turbo -I../../third_party/iccjpeg -I../../third_party/libpng -I../../third_party/zlib -I../../third_party/ots/include -I../../v8/include -Igen/v8/include -I../../third_party/angle/include -I../../third_party/angle/src/common/third_party/base -Igen/angle -I../../third_party/libxml/src/include -I../../third_party/libxml/linux/include -I../../third_party/libxslt/src -I../../third_party/snappy/src -I../../third_party/snappy/linux -fno-strict-aliasing -fno-unwind-tables -fno-asynchronous-unwind-tables -fPIC -pipe -B../../third_party/binutils/Linux_x64/Release/bin -pthread -fcolor-diagnostics -fdebug-prefix-map=/b/c/b/Google_Chrome_ChromeOS/src=. -no-canonical-prefixes -m64 -march=x86-64 -Wall -Werror -Wextra -Wno-missing-field-initializers -Wno-unused-parameter -Wno-c++11-narrowing -Wno-covered-switch-default -Wno-unneeded-internal-declaration -Wno-inconsistent-missing-override -Wno-undefined-var-template -Wno-nonportable-include-path -Wno-address-of-packed-member -Wno-unused-lambda-capture -Wno-user-defined-warnings -Wno-enum-compare-switch -Wno-tautological-unsigned-zero-compare -Wno-null-pointer-arithmetic -Wno-tautological-unsigned-enum-zero-compare -O2 -fno-ident -fdata-sections -ffunction-sections -fno-omit-frame-pointer -g2 -ggnu-pubnames -fvisibility=hidden -Xclang -load -Xclang ../../third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.so -Xclang -add-plugin -Xclang find-bad-constructs -Xclang -plugin-arg-find-bad-constructs -Xclang check-ipc -Wheader-hygiene -Wstring-conversion -Wtautological-overlap-compare -Wexit-time-destructors -Xclang -load -Xclang ../../third_party/llvm-build/Release+Asserts/lib/libBlinkGCPlugin.so -Xclang -add-plugin -Xclang blink-gc-plugin -Wglobal-constructors -Wno-header-guard -DLIBXML_STATIC= -std=gnu++14 -fno-rtti -nostdinc++ -isystem../../buildtools/third_party/libc++/trunk/include -isystem../../buildtools/third_party/libc++abi/trunk/include --sysroot=../../build/linux/debian_jessie_amd64-sysroot -fno-exceptions -fvisibility-inlines-hidden -c ../../third_party/WebKit/Source/core/page/PageWidgetDelegate.cpp -o obj/third_party/WebKit/Source/core/page/page/PageWidgetDelegate.o
In file included from ../../third_party/WebKit/Source/core/page/PageWidgetDelegate.cpp:45:
In file included from ../../third_party/WebKit/Source/platform/graphics/paint/DrawingRecorder.h:13:
../../third_party/WebKit/Source/platform/graphics/paint/DrawingDisplayItem.h:30:3: error: [chromium-style] Complex constructor has an inlined body.
  DISABLE_CFI_PERF
  ^
../../base/compiler_specific.h:184:26: note: expanded from macro 'DISABLE_CFI_PERF'
#define DISABLE_CFI_PERF __attribute__((no_sanitize("cfi")))
        
I suspect what's happening is the SourceLocation for the constructor points to DISABLE_CFI_PERF. When checking whether or not to emit a warning, we use the spelling loc--and since this is a macro, we use the SourceLocation from //base--where we do enable all errors.

This broke in the clang roll, since the plugin changed to no longer force Blink to skip all checks. We currently use the spelling loc because we don't want to emit warnings if it's due to a macro from a system header that we can't do anything about. Perhaps we need to find a better SourceLocation for the ctor or reconsider use of the spelling loc.