Add a GN build configuration for controlling stack frame generation.

This is part 1 of staging crrev.com/2266073002.

Part 1: Add empty config("default_stack_frames").
Part 2: Disable this config in third_party/ffmpeg.
Part 3: Move Chromium -fomit/-fno-omit-frame-pointer logic into this config.

TBR=brettw@chromium.org
TBR=dpranke@chromium.org
BUG=636489

Review-Url: https://codereview.chromium.org/2280533004
Cr-Commit-Position: refs/heads/master@{#414618}

build/config/BUILDCONFIG.gn

@@ -473,6 +473,7 @@ default_compiler_configs = [
   "//build/config/compiler:chromium_code",
   "//build/config/compiler:default_include_dirs",
   "//build/config/compiler:default_optimization",
+  "//build/config/compiler:default_stack_frames",
   "//build/config/compiler:default_symbols",
   "//build/config/compiler:no_rtti",
   "//build/config/compiler:runtime_library",

build/config/compiler/BUILD.gn

@@ -1311,6 +1311,9 @@ if (is_win) {
   }
 }
 
+config("default_stack_frames") {
+}
+
 # Default "optimization on" config.
 config("optimize") {
   if (is_win) {