Add src_files to src_jar GN template

net/android/BUILD.gn

Index: net/android/BUILD.gn
diff --git a/net/android/BUILD.gn b/net/android/BUILD.gn
index fc51171a7827323b802247ab8fa9a7833fa824a2..94e67eb3c98f2fc10fd83a66d1993a753b99af97 100644
--- a/net/android/BUILD.gn
+++ b/net/android/BUILD.gn
@@ -6,7 +6,20 @@ import("//build/config/android/config.gni")
 import("//build/config/android/rules.gni")
 
 android_library("net_java") {
-  java_files = [
+  deps = [
+    "//base:base_java",
+    "//third_party/android_tools:android_support_annotations_java",
+  ]
+  srcjar_deps = [
+    ":net_errors_java",
+    ":net_java_srcjar",
+    ":net_android_java_enums_srcjar",
+  ]
+}
+
+# Creates srcjar that contains sources for "net_java".
+zip("net_java_srcjar") {
+  inputs = [
     "java/src/org/chromium/net/AndroidCellularSignalStrength.java",
     "java/src/org/chromium/net/AndroidCertVerifyResult.java",
     "java/src/org/chromium/net/AndroidKeyStore.java",
@@ -23,14 +36,8 @@ android_library("net_java") {
     "java/src/org/chromium/net/RegistrationPolicyApplicationStatus.java",
     "java/src/org/chromium/net/X509Util.java",
   ]
-  deps = [
-    "//base:base_java",
-    "//third_party/android_tools:android_support_annotations_java",
-  ]
-  srcjar_deps = [
-    ":net_errors_java",
-    ":net_android_java_enums_srcjar",
-  ]
+  output = "$target_gen_dir/$target_name.srcjar"
+  base_dir = rebase_path("//net/android/java/src")
 }
 
 android_aidl("embedded_test_server_aidl") {