Generalize patch_project to patch root conversion.

recipe_modules/bot_update/example.expected/tryjob_gerrit_angle.json

Index: recipe_modules/bot_update/example.expected/tryjob_gerrit_angle.json
diff --git a/recipe_modules/bot_update/example.expected/gerrit_no_reset.json b/recipe_modules/bot_update/example.expected/tryjob_gerrit_angle.json
similarity index 78%
copy from recipe_modules/bot_update/example.expected/gerrit_no_reset.json
copy to recipe_modules/bot_update/example.expected/tryjob_gerrit_angle.json
index 734b43e5a1be69c7e8284e7f20fb6771712de613..b4b7311f18fd03334ccc8f02bdde247d817bfc54 100644
--- a/recipe_modules/bot_update/example.expected/gerrit_no_reset.json
+++ b/recipe_modules/bot_update/example.expected/tryjob_gerrit_angle.json
@@ -5,24 +5,29 @@
       "-u",
       "RECIPE_MODULE[depot_tools::bot_update]/resources/bot_update.py",
       "--master",
-      "experimental",
+      "chromium.testing.master",
       "--builder",
-      "Experimental Builder",
+      "TestBuilder",
       "--slave",
-      "somehost",
+      "TestSlavename",
       "--spec",
       "cache_dir = '[GIT_CACHE]'\nsolutions = [{'deps_file': '.DEPS.git', 'managed': True, 'name': 'src', 'url': 'svn://svn.chromium.org/chrome/trunk/src'}]",
       "--root",
-      "src",
+      "src/third_party/angle",
       "--revision_mapping_file",
       "{\"src\": \"got_cr_revision\"}",
       "--git-cache-dir",
       "[GIT_CACHE]",
+      "--gerrit_repo",
+      "https://chromium.googlesource.com/angle/angle",
+      "--gerrit_ref",
+      "refs/changes/11/338811/3",
       "--output_json",
       "/path/to/tmp/json",
       "--revision",
       "src@HEAD",
-      "--gerrit_no_reset"
+      "--revision",
+      "src/third_party/angle@HEAD"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {