Jumbo for blink/core generated files as well (saving 8 CPU minutes)

build/config/jumbo.gni

Index: build/config/jumbo.gni
diff --git a/build/config/jumbo.gni b/build/config/jumbo.gni
index 4a5f22f4a94ee0d2937adbe6ef5088857679df44..f98d385b9765c190690a70342a3899259e4d42f4 100644
--- a/build/config/jumbo.gni
+++ b/build/config/jumbo.gni
@@ -7,7 +7,7 @@ import("//build/split_static_library.gni")  # When someone uses that target_type
 declare_args() {
   # If true, use a jumbo build (files compiled together) to speed up
   # compilation.
-  use_jumbo_build = false
+  use_jumbo_build = !is_official_build && !(is_android && !is_clang)

[Dirk Pranke, 2017/07/07 20:12:10]

I'm guessing this change isn't intentional (or at least, isn't meant for
landing)?

[Daniel Bratell, 2017/07/10 09:18:29]

I'm adding and removing this in every CL to verify that the changes work on all
platforms. It would be nice to land but I understand the need to be careful.

 
   # A target to exclude from jumbo builds, for optimal round trip time
   # when frequently changing a single cpp file.
@@ -66,6 +66,19 @@ template("jumbo_target") {
   invoker_sources = invoker.sources
   gen_target_dir = get_path_info(invoker_sources[0], "gen_dir")
   assert(excluded_sources != [] || true)  # Prevent "unused variable".
+
+  # Find the gen_target_dir directory with shortest path.

[Dirk Pranke, 2017/07/07 20:12:10]

This is a bit obscure. Can you add more to the comment about what this is
actually doing, and why we need to do it (e.g., link to the ninja bug)? 

Is there maybe something we should be doing in GN to make sure we get the
shortest path here, instead?

[Daniel Bratell, 2017/07/10 09:18:30]

I've expanded the comment.

The part I missed in gn for this to be smoother was a len() operator to tell me
the length of a string, or actually, I'd need the number of / and \ in a string.
The most generic operator that would help would be one that said if a path was a
"parent" of another path.

+  foreach(source_file, invoker.sources) {
+    possibly_better_gen_target_dir = get_path_info(gen_target_dir, "dir")
+    possibly_better_gen_target_dir_2 =
+        get_path_info(possibly_better_gen_target_dir, "dir")
+    alt_gen_target_dir = get_path_info(source_file, "gen_dir")
+    if (alt_gen_target_dir == possibly_better_gen_target_dir ||
+        alt_gen_target_dir == possibly_better_gen_target_dir_2) {
+      gen_target_dir = alt_gen_target_dir
+    }
+  }
+
   assert(gen_target_dir != "")  # Prevent "unused variable".
 
   if (use_jumbo_build_for_target) {