[Chromecast] Set symbol_level=2 for Chromecast builds 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/chrome_build.gni")
+import("//build/config/chromecast_build.gni")
 import("//build/config/sanitizers/sanitizers.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.
   #   0 means no symbols.
   #   -1 means auto-set according to debug/release and platform.
   symbol_level = -1
 
   # Compile in such a way as to enable profiling of the generated code. For
   # example, don't omit the frame pointer and leave in symbols.
   enable_profiling = false
 }
 
 # 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_linux || (is_debug || is_official_build)) {
+  } else if (!is_linux || is_debug || is_official_build || is_chromecast) {

[alokp, 2016/03/14 16:48:23]

This is OK, but can you explain what is wrong with setting this flag explicitly
in our makefile?

[slan, 2016/03/14 17:00:36]

This solution also ensures this behavior on Android and desktop Cast builds,
which the Makefile solution does not. Without this, we have to set this flag
explicitly to get stack traces on Eng and Release builds.

[alokp, 2016/03/14 17:13:53]

I am assuming that this only affects Eng builds, right? Because both Debug and
User builds should be handled by is_debug and is_official_build, respectively?
Not sure how important it is to set it for desktop release builds.

What is the issue with Android?

Note that I am not opposed to this patch, just trying to understand the need
before adding chromecast bits in a chromium-wide file.

     # Linux is slowed 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.
+    # 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
   }
 }