Revert "Use only Gerrit.install as a plugin loaded signal"

This reverts commit 81b58f8a71.

Reason for revert: This seems to be the cause of issue 7415, where some
HTML style plugins would not load. Whereas this change reduces the
number of times that `_pluginsPending` is decremented, following this
change, the value is not decremented enough. Have locally reproduced the
error and found reverting this change fixes style plugin loading.

Change-Id: Iabe99284fbc5f0837aa9c41f20aff8fe8430d735

polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata-it_test.html

@@ -93,8 +93,7 @@ limitations under the License.
           plugin: {
             js_resource_paths: [],
             html_resource_paths: [
-              new URL('test/plugin.html?' + Math.random(),
-                      window.location.href).toString(),
+              new URL('test/plugin.html', window.location.href).toString(),
             ],
           },
         };

polygerrit-ui/app/elements/plugins/gr-endpoint-decorator/gr-endpoint-decorator_test.html

@@ -24,8 +24,6 @@ limitations under the License.
 <link rel="import" href="gr-endpoint-decorator.html">
 <link rel="import" href="../gr-endpoint-param/gr-endpoint-param.html">
 
-<script>void(0);</script>
-
 <test-fixture id="basic">
   <template>
     <gr-endpoint-decorator name="foo">

polygerrit-ui/app/elements/plugins/gr-plugin-host/gr-plugin-host.js

@@ -47,10 +47,12 @@
      * States that it expects no more than 3 parameters, but that's not true.
      * @todo (beckysiegel) check Polymer annotations and submit change.
      */
+
     _importHtmlPlugins(plugins) {
       for (const url of plugins) {
         this.importHref(
-            this._urlFor(url), null, Gerrit._pluginInstalled, true);
+            this._urlFor(url), Gerrit._pluginInstalled, Gerrit._pluginInstalled,
+            true);
       }
     },
 

polygerrit-ui/app/elements/plugins/gr-plugin-host/gr-plugin-host_test.html

@@ -23,8 +23,6 @@ limitations under the License.
 <link rel="import" href="../../../test/common-test-setup.html"/>
 <link rel="import" href="gr-plugin-host.html">
 
-<script>void(0);</script>
-
 <test-fixture id="basic">
   <template>
     <gr-plugin-host></gr-plugin-host>
@@ -63,9 +61,9 @@ limitations under the License.
         plugin: {html_resource_paths: ['foo/bar', 'baz']},
       };
       assert.isTrue(element.importHref.calledWith(
-          '/foo/bar', null, Gerrit._pluginInstalled, true));
+          '/foo/bar', Gerrit._pluginInstalled, Gerrit._pluginInstalled, true));
       assert.isTrue(element.importHref.calledWith(
-          '/baz', null, Gerrit._pluginInstalled, true));
+          '/baz', Gerrit._pluginInstalled, Gerrit._pluginInstalled, true));
     });
 
     test('imports relative html plugins from config with a base url', () => {
@@ -73,9 +71,11 @@ limitations under the License.
       element.config = {
         plugin: {html_resource_paths: ['foo/bar', 'baz']}};
       assert.isTrue(element.importHref.calledWith(
-          '/the-base/foo/bar', null, Gerrit._pluginInstalled, true));
+          '/the-base/foo/bar', Gerrit._pluginInstalled, Gerrit._pluginInstalled,
+          true));
       assert.isTrue(element.importHref.calledWith(
-          '/the-base/baz', null, Gerrit._pluginInstalled, true));
+          '/the-base/baz', Gerrit._pluginInstalled, Gerrit._pluginInstalled,
+          true));
     });
 
     test('imports absolute html plugins from config', () => {
@@ -88,9 +88,11 @@ limitations under the License.
         },
       };
       assert.isTrue(element.importHref.calledWith(
-          'http://example.com/foo/bar', null, Gerrit._pluginInstalled, true));
+          'http://example.com/foo/bar', Gerrit._pluginInstalled,
+          Gerrit._pluginInstalled, true));
       assert.isTrue(element.importHref.calledWith(
-          'https://example.com/baz', null, Gerrit._pluginInstalled, true));
+          'https://example.com/baz', Gerrit._pluginInstalled,
+          Gerrit._pluginInstalled, true));
     });
 
     test('adds js plugins from config to the body', () => {
@@ -137,9 +139,9 @@ limitations under the License.
         },
       };
       assert.isTrue(element.importHref.calledWith(
-          '/oof', null, Gerrit._pluginInstalled, true));
+          '/oof', Gerrit._pluginInstalled, Gerrit._pluginInstalled, true));
       assert.isTrue(element.importHref.calledWith(
-          '/some', null, Gerrit._pluginInstalled, true));
+          '/some', Gerrit._pluginInstalled, Gerrit._pluginInstalled, true));
     });
   });
 </script>