Supersize: Store whether source path was generated in flags

tools/binary_size/libsupersize/testdata/FullDescription.golden

 Metadata:
     elf_arch=ARM
     elf_build_id=WhatAnAmazingBuildId
     elf_file_name=elf
     elf_mtime={redacted}
     git_revision=abc123
     gn_args=var1=true var2="foo"
     map_file_name=../test.map
 
 Section Sizes (Total=43,785,380 bytes):
@@ skipping 84 matching lines @@
              source_path=       object_path=
              flags={}  name=** symbol gap 3 (end of section)
 43613305 d@0x2c17740  pss=789904  padding=0  size_without_padding=789904
              source_path=third_party/container.c        object_path=third_party/WebKit.a/ContiguousContainer.o
              flags={}  name=chrome::mojom::FieldTrialRecorderProxy [vtable]
 43714905 d@0x2dffd88  pss=101600  padding=101600  size_without_padding=0
              source_path=       object_path=
              flags={}  name=** symbol gap 3 (end of section)
 43784029 t@0x28f1e0   pss=69124  padding=4  size_without_padding=69120
              source_path=third_party/icu/ucnv_ext.c     object_path=third_party/icu/icuuc/ucnv_ext.o
-             flags={unlikely}  name=foo_bar
+             flags={unlikely,gen}  name=foo_bar
 43784477 t@0x28f000   pss=448  padding=0  size_without_padding=448
              source_path=third_party/icu/ucnv_ext.c     object_path=third_party/icu/icuuc/ucnv_ext.o
-             flags={}  name=ucnv_extMatchFromU
+             flags={gen}  name=ucnv_extMatchFromU
                         full_name=ucnv_extMatchFromU(int const*, int, unsigned short const*, int, unsigned short const*, int, unsigned int*, signed char, signed char)
 43784629 d@0x2de7008  pss=152  padding=0  size_without_padding=152
              source_path=third_party/container.c        object_path=third_party/WebKit.a/ContiguousContainer.o
              flags={rel}  name=base::android::kBaseRegisteredMethods
 43784723 t@0x2a1000   pss=94  padding=0  size_without_padding=94
              source_path=third_party/container.c        object_path=third_party/WebKit.a/ContiguousContainer.o
              flags={anon}  name=blink::PaintChunker::releasePaintChunks [clone .part.1]
                         full_name=blink::PaintChunker::releasePaintChunks() [clone .part.1]
 43784779 d@0x2c176f0  pss=56  padding=0  size_without_padding=56
              source_path=third_party/icu/ucnv_ext.c     object_path=third_party/icu/icuuc/ucnv_ext.o
-             flags={}  name=ChromeMainDelegate [vtable]
+             flags={gen}  name=ChromeMainDelegate [vtable]
 43784835 d@0x2cd8500  pss=56  padding=0  size_without_padding=56
              source_path=third_party/paint.cc   object_path=third_party/WebKit.a/PaintChunker.o
              flags={}  name=ChromeMainDelegateAndroid [vtable]
 43784891 t@0x28d910   pss=56  padding=0  size_without_padding=56
              source_path=base/page_allocator.cc         object_path=base/base/page_allocator.o
              flags={startup}  name=_GLOBAL__sub_I_bbr_sender.cc
 43784946 r@0x28f3450  pss=55  padding=7  size_without_padding=48
              source_path=third_party/paint.cc   object_path=third_party/WebKit.a/PaintChunker.o
              flags={anon}  name=kAnimationFrameTimeHistogramClassPath
 43784970 t@0x2a0000   pss=24  padding=32  size_without_padding=16
              source_path=third_party/icu/ucnv_ext.c     object_path=third_party/icu/icuuc/ucnv_ext.o
-             flags={2 aliases}  name=BazAlias
+             flags={gen,2 aliases}  name=BazAlias
                         full_name=BazAlias(bool)
 43784994 t@0x2a0000   pss=24  padding=32  size_without_padding=16
              source_path=       object_path=
              flags={2 aliases}  name=blink::ContiguousContainerBase::shrinkToFit
                         full_name=blink::ContiguousContainerBase::shrinkToFit()
 43785038 r@0x284e370  pss=44  padding=4  size_without_padding=40
              source_path=base/page_allocator.cc         object_path=base/base/page_allocator.o
              flags={}  name=Name
 43785076 t@0x28d964   pss=38  padding=0  size_without_padding=38
              source_path=base/page_allocator.cc         object_path=base/base/page_allocator.o
              flags={}  name=extFromUUseMapping
                         full_name=extFromUUseMapping(signed char, unsigned int, int)
 43785108 d@0x2cd84e0  pss=32  padding=16  size_without_padding=16
              source_path=       object_path=third_party/gvr-android-sdk/libgvr_shim_static_arm.a/libcontroller_api_impl.a_controller_api_impl.o
              flags={}  name=.Lswitch.table.45
 43785140 r@0x284e398  pss=32  padding=0  size_without_padding=32
              source_path=third_party/container.c        object_path=third_party/WebKit.a/ContiguousContainer.o
              flags={}  name=chrome::mojom::FilePatcher::Name_
 43785172 t@0x28d98a   pss=32  padding=0  size_without_padding=32
              source_path=base/page_allocator.cc         object_path=base/base/page_allocator.o
              flags={}  name=extFromUUseMapping
                         full_name=extFromUUseMapping(aj, int)
 43785200 t@0x28f1c8   pss=28  padding=8  size_without_padding=20
              source_path=third_party/icu/ucnv_ext.c     object_path=third_party/icu/icuuc/ucnv_ext.o
-             flags={startup}  name=_GLOBAL__sub_I_SkDeviceProfile.cpp
+             flags={startup,gen}  name=_GLOBAL__sub_I_SkDeviceProfile.cpp
 43785228 t@0x28d948   pss=28  padding=0  size_without_padding=28
              source_path=base/page_allocator.cc         object_path=base/base/page_allocator.o
              flags={startup}  name=_GLOBAL__sub_I_pacing_sender.cc
 43785256 t@0x2a0020   pss=28  padding=4  size_without_padding=24
              source_path=third_party/container.c        object_path=third_party/WebKit.a/ContiguousContainer.o
              flags={}  name=blink::ContiguousContainerBase::ContiguousContainerBase
                         full_name=blink::ContiguousContainerBase::ContiguousContainerBase(blink::ContiguousContainerBase&&)
 43785280 d@0x2c17728  pss=24  padding=0  size_without_padding=24
              source_path=third_party/icu/ucnv_ext.c     object_path=third_party/icu/icuuc/ucnv_ext.o
-             flags={}  name=chrome::mojom::FieldTrialRecorder [vtable]
+             flags={gen}  name=chrome::mojom::FieldTrialRecorder [vtable]
 43785304 d@0x2cd8538  pss=24  padding=0  size_without_padding=24
              source_path=base/page_allocator.cc         object_path=base/base/page_allocator.o
              flags={}  name=mojo::MessageReceiver [vtable]
 43785320 t@0x28d900   pss=16  padding=0  size_without_padding=16
              source_path=base/page_allocator.cc         object_path=base/base/page_allocator.o
              flags={startup}  name=_GLOBAL__sub_I_page_allocator.cc
 43785324 t@0x2a0010   pss=4  padding=0  size_without_padding=12
              source_path=third_party/fft_float.cc       object_path=third_party/ffmpeg/libffmpeg_internal.a/fft_float.o
              flags={3 aliases}  name=BarAlias
                         full_name=BarAlias()
@@ skipping 33 matching lines @@
              source_path=third_party/fft_float.cc       object_path=third_party/ffmpeg/libffmpeg_internal.a/fft_float.o
              flags={}  name=ff_cos_131072
 43785380 b@0x0        pss=131072  padding=0  size_without_padding=131072
              source_path=third_party/fft_fixed.cc       object_path=third_party/ffmpeg/libffmpeg_internal.a/fft_fixed.o
              flags={}  name=ff_cos_131072_fixed
 43785380 b@0x0        pss=131072  padding=0  size_without_padding=131072
              source_path=third_party/fft_float.cc       object_path=third_party/ffmpeg/libffmpeg_internal.a/fft_float.o
              flags={}  name=ff_cos_65536
 43785380 b@0x2dffe80  pss=200  padding=196  size_without_padding=4
              source_path=third_party/icu/ucnv_ext.c     object_path=third_party/icu/icuuc/ucnv_ext.o
-             flags={}  name=SaveHistogram::atomic_histogram_pointer
+             flags={gen}  name=SaveHistogram::atomic_histogram_pointer
                         full_name=SaveHistogram(_JNIEnv*, base::android::JavaParamRef<_jobject*> const&, base::android::JavaParamRef<_jstring*> const&, base::android::JavaParamRef<_jlongArray*> const&, int)::atomic_histogram_pointer
 43785380 b@0x2dffda0  pss=28  padding=0  size_without_padding=28
              source_path=third_party/icu/ucnv_ext.c     object_path=third_party/icu/icuuc/ucnv_ext.o
-             flags={}  name=g_chrome_content_browser_client
+             flags={gen}  name=g_chrome_content_browser_client
 43785380 b@0x2dffe84  pss=4  padding=0  size_without_padding=4
              source_path=third_party/icu/ucnv_ext.c     object_path=third_party/icu/icuuc/ucnv_ext.o
-             flags={anon}  name=g_AnimationFrameTimeHistogram_clazz
+             flags={anon,gen}  name=g_AnimationFrameTimeHistogram_clazz