Keep unwind table when cast_is_debug is true

The platform of Chromecast devices are arm/aarch64. For getting the
backtrace of malloc location by heap profiler, we need to keep the
unwind table for stack walking.

Bug: None
Change-Id: I8e4e4dc4f47206734aa7764a956c751c825446e2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1527952
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Commit-Queue: Chia-hung Duan <chiahungduan@google.com>
Auto-Submit: Chia-hung Duan <chiahungduan@google.com>
Cr-Original-Commit-Position: refs/heads/master@{#642465}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: e0837a9674eeab95a1c5872f4328f18e447558b2

config/chromecast_build.gni

@@ -10,6 +10,11 @@ declare_args() {
   # Linux and Android.
   is_chromecast = false
 
+  # If true, IS_CAST_DEBUG_BUILD() will evaluate to 1 in version.h. Otherwise,
+  # it will evaluate to 0. Overriding this when is_debug=false is useful for
+  # doing engineering builds.
+  cast_is_debug = is_debug
+
   # chromecast_branding is used to include or exclude Google-branded components.
   # Set it to "public" for a Chromium build.
   chromecast_branding = "public"

config/compiler/compiler.gni

@@ -83,9 +83,9 @@ assert(!is_cfi || use_thin_lto, "CFI requires ThinLTO")
 # For unofficial (e.g. development) builds and non-Chrome branded (e.g. Cronet
 # which doesn't use Crashpad, crbug.com/479283) builds it's useful to be able
 # to unwind at runtime.
-exclude_unwind_tables =
-    (is_chrome_branded && is_official_build) ||
-    (is_chromecast && !is_cast_desktop_build && !is_debug && !is_fuchsia)
+exclude_unwind_tables = (is_chrome_branded && is_official_build) ||
+                        (is_chromecast && !is_cast_desktop_build && !is_debug &&
+                         !cast_is_debug && !is_fuchsia)
 
 # If true, optimize for size. Does not affect windows builds.
 # Linux & Mac favor speed over size.