[Android WebAPK Refactor] Introduce way to define config JSON file as delta

This CL introduces a way of defining a JSON config file as a "base JSON
config file" + "delta config file".
The generated config follows the following rules:
- If a key is present in both the "base config" and the "delta config" the
  value in the "delta config" is used.
- If a key is present in one of the "base config" and the "delta config"
  the key+value are included in the generated config.

The reason for this change are to:
1) Make it easier to add test configs
2) Avoid breakages due to the configs being out of sync such as
https://chromium-review.googlesource.com/c/chromium/src/+/1298428

BUG=899274

Change-Id: I48f236c4d6a86cba32c144b773ba6aab8c99b783
Reviewed-on: https://chromium-review.googlesource.com/c/1302326
Commit-Queue: Peter Kotwicz <pkotwicz@chromium.org>
Reviewed-by: agrieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603282}

chrome/android/webapk/shell_apk/BUILD.gn

@@ -98,6 +98,7 @@ template("webapk_tmpl") {
                            [
                              "apk_package_name",
                              "config_file",
+                             "delta_config_file",
                            ])
 
     input = _manifest_to_upload_output
@@ -229,7 +230,8 @@ webapk_tmpl("unbound_webapk") {
 }
 
 webapk_tmpl("http_webapk") {
-  config_file = "manifest/http_manifest_config.json"
+  config_file = "manifest/bound_manifest_config.json"
+  delta_config_file = "manifest/http_manifest_config_delta.json"
   apk_name = "HttpWebApk"
   apk_package_name = "org.chromium.webapk.http"
 }

chrome/android/webapk/shell_apk/manifest/http_manifest_config.json

-{
-  "scope_url": "http://pwa.rocks/",
-  "intent_filters": {
-    "scope_url_scheme": "http",
-    "scope_url_host": "pwa.rocks",
-    "scope_url_path_type": "android:pathPrefix",
-    "scope_url_path": "/"
-  },
-  "start_url": "http://pwa.rocks/",
-  "display_mode": "standalone",
-  "orientation": "portrait",
-  "theme_color": "2147483648L",
-  "background_color": "2147483648L",
-  "has_large_splash_icons": "false",
-  "icon_urls_and_icon_murmur2_hashes": "http://www.pwa.rocks/icon1.png 0 http://www.pwa.rocks/icon2.png 0",
-  "web_manifest_url": "https://pwa.rocks/pwa.webmanifest",
-  "distributor": "browser",
-  "version_code": "1",
-  "version_name": "1.0",
-  "bound_webapk": {
-    "runtime_host": "com.google.android.apps.chrome",
-    "runtime_host_application_name": "Chromium"
-  },
-  "share_template": [{
-	  "index": "0",
-	  "title": "Share All",
-	  "action": "http://pwa.rocks/share.html",
-	  "param_title": "title",
-	  "param_text": "text",
-	  "param_url": "url"
-  },
-  {
-	  "index": "1",
-	  "title": "Share Title",
-	  "action": "http://pwa.rocks/share_title.html",
-	  "param_title": "title",
-	  "param_text": "text",
-	  "param_url": "url"
-  }]
-}

chrome/android/webapk/shell_apk/manifest/http_manifest_config_delta.json

+{
+  "scope_url": "http://pwa.rocks/",
+  "intent_filters": {
+    "scope_url_scheme": "http",
+    "scope_url_host": "pwa.rocks",
+    "scope_url_path_type": "android:pathPrefix",
+    "scope_url_path": "/"
+  },
+  "start_url": "http://pwa.rocks/"
+}

chrome/android/webapk/shell_apk/manifest/manifest_mustache_pass.gni

@@ -23,6 +23,10 @@ template("manifest_mustache_pass") {
     if (defined(invoker.config_file)) {
       sources += [ invoker.config_file ]
     }
+    if (defined(invoker.delta_config_file)) {
+      sources += [ invoker.delta_config_file ]
+    }
+
     script =
         "//chrome/android/webapk/shell_apk/manifest/manifest_mustache_pass.py"
 
@@ -42,6 +46,12 @@ template("manifest_mustache_pass") {
         rebase_path(invoker.config_file, root_build_dir),
       ]
     }
+    if (defined(invoker.delta_config_file)) {
+      args += [
+        "--delta_config_file",
+        rebase_path(invoker.delta_config_file, root_build_dir),
+      ]
+    }
     if (defined(invoker.extra_variables)) {
       extra_variables = invoker.extra_variables
       args += [ "--extra_variables=${extra_variables}" ]

chrome/android/webapk/shell_apk/manifest/manifest_mustache_pass.py

@@ -32,6 +32,7 @@ def _AppendParsedVariables(initial_variable_list, variables_arg, error_func):
     variables[name] = value
   return variables
 
+
 def main():
   parser = argparse.ArgumentParser()
   parser.add_argument('--template', required=True,
@@ -40,6 +41,8 @@ def main():
                       help='The output file to generate.')
   parser.add_argument('--config_file',
                       help='JSON file with values to put into template.')
+  parser.add_argument('--delta_config_file', help='JSON file with '
+                      'substitutions to |config_file|.')
   parser.add_argument('--extra_variables', help='Variables to be made '
                       'available in the template processing environment (in '
                       'addition to those specified in config file), as a GN '
@@ -47,10 +50,15 @@ def main():
                       default='')
   options = parser.parse_args()
 
-  variables = {}
+  config = {}
   if options.config_file:
     with open(options.config_file, 'r') as f:
-      variables = json.loads(f.read())
+      config = json.loads(f.read())
+  if options.delta_config_file:
+    with open(options.delta_config_file, 'r') as f:
+      config.update(json.loads(f.read()))
+
+  variables = config
   variables = _AppendParsedVariables(variables, options.extra_variables,
                                      parser.error)