Output a linker map file for official builds

build/toolchain/gcc_toolchain.gni

Index: build/toolchain/gcc_toolchain.gni
diff --git a/build/toolchain/gcc_toolchain.gni b/build/toolchain/gcc_toolchain.gni
index b31980668d89732523e9765f83e2e24f7caf1a4d..0fd83444b3b7b331f6fa4a04a3ce90c294361793 100644
--- a/build/toolchain/gcc_toolchain.gni
+++ b/build/toolchain/gcc_toolchain.gni
@@ -319,18 +319,26 @@ template("gcc_toolchain") {
 
       link_command = "$ld -shared {{ldflags}}${extra_ldflags} -o \"$unstripped_sofile\" -Wl,-soname=\"$soname\" @\"$rspfile\""
 
+      # Generate a map file to be used for binary size analysis.
+      # Map file adds ~10% to the link time on a z620.
+      # With target_os="android", libchrome.so.map.gz is ~20MB.
+      map_switch = ""
+      if (is_official_build) {

[Dirk Pranke, 2017/03/03 21:38:48]

This'll affect linux and chromeos too, right? Is that intentional? For Linux,
due to LTO, a 10% impact is not small.

[agrieve, 2017/03/04 02:01:26]

It was intentional, since the size analysis tool should work just the same on
these other platforms as well.

On one hand, I can certainly get quite far by making this android only.
OTOH, my 10% number came from adding 3 seconds to my 30 second link. I suspect
it would also add around 3 seconds to an lto link, which wouldn't be too bad.

+        map_switch = "--mapfile \"$unstripped_sofile.map.gz\" "
+      }
+
       assert(defined(readelf), "to solink you must have a readelf")
       assert(defined(nm), "to solink you must have an nm")
       strip_switch = ""
       if (defined(invoker.strip)) {
-        strip_switch = "--strip=${invoker.strip}"
+        strip_switch = "--strip=${invoker.strip} "
       }
 
       # This needs a Python script to avoid using a complex shell command
       # requiring sh control structures, pipelines, and POSIX utilities.
       # The host might not have a POSIX shell and utilities (e.g. Windows).
       solink_wrapper = rebase_path("//build/toolchain/gcc_solink_wrapper.py")
-      command = "$python_path \"$solink_wrapper\" --readelf=\"$readelf\" --nm=\"$nm\" $strip_switch --sofile=\"$unstripped_sofile\" --tocfile=\"$tocfile\" --output=\"$sofile\"$whitelist_flag -- $link_command"
+      command = "$python_path \"$solink_wrapper\" --readelf=\"$readelf\" --nm=\"$nm\" $strip_switch--sofile=\"$unstripped_sofile\" --tocfile=\"$tocfile\" $map_switch--output=\"$sofile\"$whitelist_flag -- $link_command"
 
       rspfile_content = "-Wl,--whole-archive {{inputs}} {{solibs}} -Wl,--no-whole-archive $solink_libs_section_prefix {{libs}} $solink_libs_section_postfix"