Add support for GNU GLOBAL.

Makefile

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 391 matching lines @@
         rm -rf $(OUTDIR)/$(basename $@).release
         rm -rf $(OUTDIR)/$(basename $@).debug
         rm -rf $(OUTDIR)/$(basename $@).optdebug
         find $(OUTDIR) -regex '.*\(host\|target\)\.$(basename $@).*\.mk' -delete
 
 native.clean:
         rm -f $(OUTDIR)/Makefile.native
         rm -rf $(OUTDIR)/native
         find $(OUTDIR) -regex '.*\(host\|target\)\.native\.mk' -delete
 
-clean: $(addsuffix .clean, $(ARCHES) $(ANDROID_ARCHES) $(NACL_ARCHES)) native.clean
+clean: $(addsuffix .clean, $(ARCHES) $(ANDROID_ARCHES) $(NACL_ARCHES)) native.clean gtags.clean
 
 # GYP file generation targets.
 OUT_MAKEFILES = $(addprefix $(OUTDIR)/Makefile.,$(BUILDS))
 $(OUT_MAKEFILES): $(GYPFILES) $(ENVFILE)
         PYTHONPATH="$(shell pwd)/tools/generate_shim_headers:$(PYTHONPATH)" \
         PYTHONPATH="$(shell pwd)/build/gyp/pylib:$(PYTHONPATH)" \
         GYP_GENERATORS=make \
         build/gyp/gyp --generator-output="$(OUTDIR)" build/all.gyp \
                       -Ibuild/standalone.gypi --depth=. \
                       -Dv8_target_arch=$(subst .,,$(suffix $(basename $@))) \
@@ skipping 37 matching lines @@
 $(ENVFILE).new:
         @mkdir -p $(OUTDIR); echo "GYPFLAGS=$(GYPFLAGS)" > $(ENVFILE).new; \
             echo "CXX=$(CXX)" >> $(ENVFILE).new
 
 # Heap constants for grokdump.
 DUMP_FILE = tools/v8heapconst.py
 grokdump: ia32.release
         @cat $(DUMP_FILE).tmpl > $(DUMP_FILE)
         @$(OUTDIR)/ia32.release/d8 --dump-heap-constants >> $(DUMP_FILE)
 
+# Support for the GNU GLOBAL Source Code Tag System.
+gtags.files: $(GYPFILES) $(ENVFILE)
+        @find include src test -name '*.h' -o -name '*.cc' -o -name '*.c' > $@
+
+GTAGS GRTAGS GPATH: gtags.files
+        @GTAGSFORCECPP=yes gtags -i -q
+
+gtags.clean:
+        rm -f GTAGS GRTAGS GPATH gtags.files
+
 # Dependencies.
 # Remember to keep these in sync with the DEPS file.
 dependencies:
         svn checkout --force http://gyp.googlecode.com/svn/trunk build/gyp \
             --revision 1831
         svn checkout --force \
             https://src.chromium.org/chrome/trunk/deps/third_party/icu46 \
             third_party/icu --revision 258359