Revert of Enable extended debugging symbols to including better tracking....

Revert of Enable extended debugging symbols to including  better tracking. (patchset #3 id:40001 of https://codereview.chromium.org/362183003/)

Reason for revert:
Breaks with

FAILED: /b/build/goma/gomacc ../../third_party/llvm-build/Release+Asserts/bin/clang -MMD -MF obj/third_party/libwebp/enc/libwebp_enc.config.o.d -DV8_DEPRECATION_WARNINGS -D_FILE_OFFSET_BITS=64 -DCHROMIUM_BUILD -DCR_CLANG_REVISION=216630 -DCOMPONENT_BUILD -DTOOLKIT_VIEWS=1 -DUI_COMPOSITOR_IMAGE_TRANSPORT -DUSE_AURA=1 -DUSE_ASH=1 -DUSE_PANGO=1 -DUSE_CAIRO=1 -DUSE_GLIB=1 -DUSE_DEFAULT_RENDER_THEME=1 -DUSE_LIBJPEG_TURBO=1 -DUSE_X11=1 -DUSE_CLIPBOARD_AURAX11=1 -DENABLE_ONE_CLICK_SIGNIN -DENABLE_PRE_SYNC_BACKUP -DUSE_XI2_MT=2 -DENABLE_REMOTING=1 -DENABLE_WEBRTC=1 -DENABLE_PEPPER_CDMS -DENABLE_CONFIGURATION_POLICY -DENABLE_NOTIFICATIONS -DUSE_UDEV -DENABLE_EGLIMAGE=1 -DENABLE_TASK_MANAGER=1 -DENABLE_EXTENSIONS=1 -DENABLE_PLUGINS=1 -DENABLE_SESSION_SERVICE=1 -DENABLE_THEMES=1 -DENABLE_AUTOFILL_DIALOG=1 -DENABLE_BACKGROUND=1 -DENABLE_GOOGLE_NOW=1 -DCLD_VERSION=2 -DCLD2_DATA_SOURCE=static -DENABLE_FULL_PRINTING=1 -DENABLE_PRINTING=1 -DENABLE_SPELLCHECK=1 -DENABLE_CAPTIVE_PORTAL_DETECTION=1 -DENABLE_APP_LIST=1 -DENABLE_SETTINGS_APP=1 -DENABLE_MANAGED_USERS=1 -DENABLE_MDNS=1 -DENABLE_SERVICE_DISCOVERY=1 -DENABLE_LOAD_COMPLETION_HACKS=1 -DUSE_NSS=1 -DDYNAMIC_ANNOTATIONS_ENABLED=1 -DWTF_USE_DYNAMIC_ANNOTATIONS=1 -D_DEBUG -D_GLIBCXX_DEBUG=1 -Igen -I../../third_party/libwebp -fstack-protector --param=ssp-buffer-size=4 -Werror -pthread -fno-strict-aliasing -Wno-unused-parameter -Wno-missing-field-initializers -fvisibility=hidden -pipe -fPIC -Wno-reserved-user-defined-literal -Xclang -load -Xclang /b/build/slave/Linux_Builder__dbg_/build/src/third_party/llvm-build/Release+Asserts/lib/libFindBadConstructs.so -Xclang -add-plugin -Xclang find-bad-constructs -fcolor-diagnostics -B/b/build/slave/Linux_Builder__dbg_/build/src/third_party/binutils/Linux_x64/Release/bin -Wheader-hygiene -Wno-char-subscripts -Wno-unneeded-internal-declaration -Wno-covered-switch-default -Wstring-conversion -Wno-c++11-narrowing -Wno-deprecated-register -Wno-format -Wno-unused-result -m64 -march=x86-64 -O0 -g -gdwarf-4 -fvar-tracking-assignments -fvar-tracking -funwind-tables -gsplit-dwarf -Wno-undefined-bool-conversion -Wno-tautological-undefined-compare   -c ../../third_party/libwebp/enc/config.c -o obj/third_party/libwebp/enc/libwebp_enc.config.o
clang: error: unknown argument: '-fvar-tracking-assignments'
clang: error: unknown argument: '-fvar-tracking'

See http://build.chromium.org/p/chromium.linux/builders/Linux%20Builder%20%28dbg%29/builds/79150/steps/compile/logs/stdio for more info.

Original issue's description:
> Enable extended debugging symbols to including better tracking.
>
> Adding -fvar-tracking-assignments and -fvar-tracking to improve
> tracking of variables and assignments. While mostly useful when
> compiling with optimisations on (-O flags), it does help with clang
> (and later gccs) which are doing many optimisations all the time.
> (It does sometimes default to on when compiling with -O flags.)
>
> From http://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html
> > -fvar-tracking
> >  Run variable tracking pass. It computes where variables are stored
> >  at each position in code. Better debugging information is then
> >  generated (if the debugging information format supports this
> >  information).
> >
> >  It is enabled by default when compiling with optimization (-Os, -O,
> >  -O2, ...), debugging information (-g) and the debug info format
> >  supports it.
> >
> > -fvar-tracking-assignments
> >  Annotate assignments to user variables early in the compilation and
> >  attempt to carry the annotations over throughout the compilation
> >  all the way to the end, in an attempt to improve debug information
> >  while optimizing. Use of -gdwarf-4 is recommended along with it.
> >
> >  It can be enabled even if var-tracking is disabled, in which case
> >  annotations are created and maintained, but discarded at the end.
>
> Committed: https://crrev.com/9f7cb7480b85d868fb3420b960018d9137c9954a
> Cr-Commit-Position: refs/heads/master@{#296662}

TBR=thestig@chromium.org,thakis@chromium.org
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/602023002

Cr-Commit-Position: refs/heads/master@{#296664}

build/common.gypi

@@ -3569,11 +3569,6 @@
               '-gdwarf-4',
             ],
             'conditions' : [
-              ['fastbuild==0', {
-                'cflags': [
-                  '-fvar-tracking-assignments', '-fvar-tracking',
-                ],
-              }],
               ['OS=="android"', {
                 'ldflags': [
                   # Warn in case of text relocations.