View source for TPEGFX/dump b2g stack

* Dump kernel call stack
  void func()
  {
    dump_stack()
  }
* Dump user-space call stack
  android.mk:
    LOCAL_SHARED_LIBRARIES += libutils
  
  #include <utils/CallStack.h>
  void func()
  {
    ...
    android::CallStack stack;
    stack.update( );
    stack.log("XXX");  // after android 4.4
    stack.dump("XXX"); // before android 4.4
    ...
  }
* The log should like
  D/bignose ( 8131): #01 pc 00c50c53  /system/b2g/libxul.so
  D/bignose ( 8131): #02 pc 00b638e5  /system/b2g/libxul.so
  D/bignose ( 8131): #03 pc 00bbe341  /system/b2g/libxul.so
  ...
* Use addr2line
  cmd:
  cat ~/tmp/stackLog.txt | awk '{print "./prebuilts/gcc/darwin-x86/arm/arm-linux-androideabi-4.8/bin/arm-linux-androideabi-addr2line --demangle -f -e /Users/bignose/work/mozilla/gecko/git/obj/mozilla_central/gecko_obj-nexus5-l/dist/bin/libxul.so " $6}' | bash
  result:
  mozilla::dom::GenericBindingMethod(JSContext*, unsigned int, JS::Value*)
  /Users/bignose/work/mozilla/gecko/git/obj/mozilla_central/gecko_obj-nexus5-l/dom/bindings/../../../../../mozilla_central/dom/bindings/BindingUtils.cpp:2609
  CallJSNative
  /Users/bignose/work/mozilla/gecko/git/obj/mozilla_central/gecko_obj-nexus5-l/js/src/../../../../../mozilla_central/js/src/jscntxtinlines.h:235
  Interpret
  /Users/bignose/work/mozilla/gecko/git/obj/mozilla_central/gecko_obj-nexus5-l/js/src/../../../../../mozilla_central/js/src/vm/Interpreter.cpp:2955
  ...