Made --filter-string optional for emma_coverage.

build/config/android/internal_rules.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/zip.gni")
 import("//third_party/ijar/ijar.gni")
 
 assert(is_android)
@@ skipping 661 matching lines @@
         rebase_path(depfile, root_build_dir),
         "--coverage-file",
         rebase_path(_coverage_file, root_build_dir),
         "--sources-list-file",
         rebase_path(_source_dirs_listing_file, root_build_dir),
         "--source-files=$_rebased_source_files",
         "--src-root",
         rebase_path("//", root_build_dir),
         "--emma-jar",
         rebase_path(_emma_jar, root_build_dir),
-        "--filter-string",
-        emma_filter,
       ]
+
+      if (emma_filter != "") {
+        args += [
+          "--filter-string",
+          emma_filter,
+        ]
+      }
     }
   } else {
     _output_jar_target = "${target_name}__copy_jar"
     copy(_output_jar_target) {
       forward_variables_from(invoker, [ "deps" ])
 
       sources = [
         invoker.input_jar_path,
       ]
       outputs = [
@@ skipping 1515 matching lines @@
 
     args = [
       "--depfile",
       rebase_path(depfile, root_build_dir),
       "--script-output-path",
       rebase_path(generated_script, root_build_dir),
     ]
     args += test_runner_args
   }
 }