Enable emma code coverage for JUnit testcases.

build/config/android/internal_rules.gni

Index: build/config/android/internal_rules.gni
diff --git a/build/config/android/internal_rules.gni b/build/config/android/internal_rules.gni
index a11f4a04239c353b7a930115bf92955a19bbcfc7..32d698ec9913e7f402a0c784d955eacf30125f54 100644
--- a/build/config/android/internal_rules.gni
+++ b/build/config/android/internal_rules.gni
@@ -240,6 +240,15 @@ template("java_binary_script") {
       "--main-class",
       _main_class,
     ]
+    if (emma_coverage) {
+      args += [
+        "--classpath",
+        rebase_path(
+            "//third_party/android_tools_internal/sdk/tools/lib/emma.jar",
+            root_out_dir),

[mikecase (-- gone --), 2016/04/26 17:59:36]

Not 100% sure, but I think you want root_build_dir instead of root_out_dir. Im
not really clear on the difference between them, but there is some info here...
https://chromium.googlesource.com/chromium/src/+/master/tools/gn/docs/referen...

[agrieve, 2016/04/26 18:10:16]

Ah, yeah, that's true. 

The two values are different only when executing in the non-default toolchain
(e.g. host_toolchain). root_build_dir is what scripts always run in.

+      ]
+      args += [ "--noverify" ]
+    }
     if (defined(invoker.wrapper_script_args)) {
       args += [ "--" ] + invoker.wrapper_script_args
     }