Android: Add java files from android_apk targets

This allows editing android_webview_apk and android_webview_test_apk
files in android studio.

BUG=670044

Review-Url: https://codereview.chromium.org/2545793002
Cr-Original-Commit-Position: refs/heads/master@{#437056}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: c3bace8213461c2a3884b36a3b80aea0e651b15a

config/android/internal_rules.gni

@@ -2245,6 +2245,11 @@ if (enable_java_templates) {
       _accumulated_deps = invoker.deps
     }
 
+    # Caller overriding build config must have valid java sources file if it has
+    # java files.
+    assert(!defined(invoker.override_build_config) ||
+           !defined(invoker.java_files) || defined(invoker.java_sources_file))
+
     assert(defined(invoker.java_files) || defined(invoker.srcjars) ||
            defined(invoker.srcjar_deps))
     _base_path = "$target_gen_dir/$target_name"
@@ -2326,7 +2331,11 @@ if (enable_java_templates) {
       _java_files += invoker.java_files
     }
     if (_java_files != []) {
-      _java_sources_file = "$_base_path.sources"
+      if (defined(invoker.java_sources_file)) {
+        _java_sources_file = invoker.java_sources_file
+      } else {
+        _java_sources_file = "$_base_path.sources"
+      }
       write_file(_java_sources_file, rebase_path(_java_files, root_build_dir))
     }
 

config/android/rules.gni

@@ -1433,6 +1433,9 @@ if (enable_java_templates) {
     _lib_dex_path = "$base_path.dex.jar"
     _rebased_lib_dex_path = rebase_path(_lib_dex_path, root_build_dir)
     _template_name = target_name
+    if (defined(invoker.java_files)) {
+      _java_sources_file = "$base_path.sources"
+    }
 
     enable_multidex =
         defined(invoker.enable_multidex) && invoker.enable_multidex
@@ -1616,6 +1619,10 @@ if (enable_java_templates) {
       build_config = _build_config
       android_manifest = _android_manifest
 
+      if (defined(_java_sources_file)) {
+        java_sources_file = _java_sources_file
+      }
+
       deps = _android_manifest_deps
 
       if (defined(invoker.deps)) {
@@ -1782,6 +1789,9 @@ if (enable_java_templates) {
       jar_path = _jar_path
       dex_path = _lib_dex_path
       emma_never_instrument = _emma_never_instrument
+      if (defined(_java_sources_file)) {
+        java_sources_file = _java_sources_file
+      }
 
       if (defined(invoker.deps)) {
         deps += invoker.deps