Revert 271207 "Changed android toolchain to use GCC 4.8"

trunk/src/build/config/arm.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 if (cpu_arch == "arm") {
   declare_args() {
     # Version of the ARM processor when compiling on ARM. Ignored on non-ARM
     # platforms.
     arm_version = 7
 
@@ skipping 22 matching lines @@
     if (arm_float_abi == "") {
       arm_float_abi = "softfp"
     }
     arm_fpu = "vfp"
     # Thumb is a reduced instruction set available on some ARM processors that
     # has increased code density.
     arm_use_thumb = false
 
   } else if (arm_version == 7) {
     arm_arch = "armv7-a"
-    arm_tune = "generic-armv7-a"
+    arm_tune = ""
     if (arm_float_abi == "") {
       arm_float_abi = "softfp"
     }
     arm_use_thumb = true
 
     if (arm_use_neon) {
       arm_fpu = "neon"
     } else {
       arm_fpu = "vfpv3-d16"
     }
   }
 }