android: Turn on fission and symbol_level=2 by default.

build/config/compiler/compiler.gni

 # Copyright 2015 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.
 
 import("//build/config/android/config.gni")
 import("//build/config/arm.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/compiler/pgo/pgo.gni")
 import("//build/config/sanitizers/sanitizers.gni")
+import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/toolchain.gni")
 import("//build_overrides/build.gni")
 
 declare_args() {
   # How many symbols to include in the build. This affects the performance of
   # the build since the symbols are large and dealing with them is slow.
   #   2 means regular build with symbols.
   #   1 means minimal symbols, usually enough for backtraces only. Symbols with
   # internal linkage (static functions or those in anonymous namespaces) may not
@@ skipping 117 matching lines @@
                       current_cpu == "arm" || current_cpu == "arm64"))
 }
 
 # If it wasn't manually set, set to an appropriate default.
 assert(symbol_level >= -1 && symbol_level <= 2, "Invalid symbol_level")
 if (symbol_level == -1) {
   if (is_android && use_order_profiling) {
     # With instrumentation enabled, debug info puts libchrome.so over 4gb, which
     # causes the linker to produce an invalid ELF. http://crbug.com/574476
     symbol_level = 0
-  } else if (is_android && !is_component_build &&
-             !(android_64bit_target_cpu && !build_apk_secondary_abi)) {
-    # Reduce symbol level when it will cause invalid elf files to be created
-    # (due to file size). https://crbug.com/648948.
-    symbol_level = 1
   } else if (is_win && use_goma && !is_clang) {
     # goma doesn't support PDB files, so we disable symbols during goma
     # compilation because otherwise the redundant debug information generated
     # by visual studio (repeated in every .obj file) makes linker
     # memory consumption and link times unsustainable (crbug.com/630074).
     # Clang on windows does not have this issue.
     # If you use is_win_fastlink = true then you can set symbol_level = 2 when
     # using goma.
     symbol_level = 1
   } else if ((!is_nacl && !is_linux) || is_debug || is_official_build ||
              is_chromecast) {
     # Linux builds slower by having symbols as part of the target binary,
     # whereas Mac and Windows have them separate, so in Release Linux, default
     # them off, but keep them on for Official builds and Chromecast builds.
     symbol_level = 2
   } else if (using_sanitizer) {
     # Sanitizers require symbols for filename suppressions to work.
     symbol_level = 1
   } else {
     symbol_level = 0
   }
 } else if (symbol_level == 2) {
   if (is_win) {
     # See crbug.com/630074
     assert(is_win_fastlink || !use_goma,
            "Goma builds that use symbol_level 2 must use is_win_fastlink.")
   }
 }
 
+if (use_debug_fission == "default") {
+  use_debug_fission =
+      symbol_level == 2 && !is_win && use_gold && cc_wrapper == ""
+}
+
 # Assert that the configuration isn't going to hit https://crbug.com/648948.
-assert(ignore_elf32_limitations || !is_android ||
+assert(ignore_elf32_limitations || !is_android || use_debug_fission ||
            (android_64bit_target_cpu && !build_apk_secondary_abi) ||
            is_component_build || symbol_level < 2,
        "Android 32-bit non-component builds cannot have symbol_level=2 " +
            "due to 4GiB file size limit, see https://crbug.com/648948. " +
            "If you really want to try this out, " +
            "set ignore_elf32_limitations=true.")