More Mac signing script changes.

Moved call to create Brave config into config_factory.py.
Added a static method to our config creation to prevent an exception
when Chrome's config loading is attempted.

Maybe need to add code to throw an exception when provisioning profile
is not found from the env when not a development config, but development
var isn't passed into the config_factory which means we'd need to add
another patch.

Chromium change:

https://chromium.googlesource.com/chromium/src/+/f21027ab4d74ea035d98bbf6ba77e8fa148f08b5

commit f21027ab4d74ea035d98bbf6ba77e8fa148f08b5
Author: Joshua Pawlicki <[email protected]>
Date:   Mon Mar 23 17:45:15 2020 +0000

    Create an updater-specific signing pipeline.

    Bug: 926234

patches/chrome-installer-mac-signing-config_factory.py.patch

@@ -0,0 +1,13 @@
+diff --git a/chrome/installer/mac/signing/config_factory.py b/chrome/installer/mac/signing/config_factory.py
+index 0689fb6476e741b711454aeaf4ac7c20d5e4f989..c303bb474dcf4036fc1e8d8b6985af20ae2e4f62 100644
+--- a/chrome/installer/mac/signing/config_factory.py
++++ b/chrome/installer/mac/signing/config_factory.py
+@@ -8,6 +8,8 @@ def get_class():
+     # First look up the processed Chromium config.
+     from chromium_config import ChromiumCodeSignConfig
+     config_class = ChromiumCodeSignConfig
++    from signing_helper import GetBraveSigningConfig
++    config_class = GetBraveSigningConfig(config_class)
+
+     # Then search for the internal config for Google Chrome.
+     try:

script/signing_helper.py

@@ -117,16 +117,20 @@ def AddBravePartsForSigning(parts, config):
     return parts
 
 
-def GetBraveSigningConfig(config_class, development, mac_provisioning_profile=None):
-    if development:
-        return config_class
+def GetBraveSigningConfig(config_class):
+    class ConfigNonChromeBranded(config_class):
+
+        @staticmethod
+        def is_chrome_branded():
+            return False
 
-    if mac_provisioning_profile is not None:
-        provisioning_profile = mac_provisioning_profile
-    else:
-        # Retrieve provisioning profile exported by build/mac/sign_app.sh
-        provisioning_profile = os.environ['MAC_PROVISIONING_PROFILE']
-        assert len(provisioning_profile), 'MAC_PROVISIONING_PROFILE is not set'
+    config_class = ConfigNonChromeBranded
+
+    # Retrieve provisioning profile exported by build/mac/sign_app.sh
+    # If not set, then it's development config.
+    provisioning_profile = os.environ['MAC_PROVISIONING_PROFILE']
+    if !len(provisioning_profile):
+        return config_class
 
     class ProvisioningProfileCodeSignConfig(config_class):