Correct release channel policy descriptions

ChromeOsReleaseChannel is only honored if
ChromeOsReleaseChannelDelegated is False and the release channel on
devices can only be switched if ChromeOsReleaseChannel is set to True.

Update comments and policy description to match the behavior.

Bug: 1147003
Change-Id: I72436eb3d50df9755c88aeec17b099e2a3d26b23
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2549923Reviewed-by: Sergey Poromov <poromov@chromium.org>
Commit-Queue: Miriam Polzer <mpolzer@google.com>
Cr-Commit-Position: refs/heads/master@{#829595}

components/policy/proto/chrome_device_policy.proto

@@ -89,9 +89,9 @@ message ReleaseChannelProto {
   // One of "stable-channel", "beta-channel", or "dev-channel"
   optional string release_channel = 1;
 
-  // If |release_channel_delegated| is set to true and the |release_channel|
-  // field is not set or left empty, the user can select the channel. If the
-  // |release_channel| is specified it will always override users choice!
+  // The user can select the channel if |release_channel_delegated| is true.
+  // The value of |release_channel| is only taken into account if
+  // |release_channel_delegated| is set to false.
   optional bool release_channel_delegated = 2;
 
   // |release_lts_tag| is forwarded as the "ltshint" attribute to Omaha.

components/policy/resources/policy_templates.json

@@ -9689,7 +9689,9 @@
       'id': 91,
       'caption': '''Release channel''',
       'tags': [],
-      'desc': '''Specifies the release channel that this device should be locked to.''',
+      'desc': '''Specifies the release channel that this device should be locked to.
+
+      Setting <ph name="CHROME_OS_RELEASE_CHANNEL_POLICY_NAME">ChromeOsReleaseChannel</ph> only has an effect if <ph name="CHROME_OS_RELEASE_CHANNEL_DELEGATED_POLICY_NAME">ChromeOsReleaseChannelDelegated</ph> is set to False.''',
     },
     {
       'name': 'ChromeOsReleaseChannelDelegated',
@@ -9705,9 +9707,9 @@
       'id': 134,
       'caption': '''Users may configure the Chrome OS release channel''',
       'tags': [],
-      'desc': '''If this policy is set to True and the ChromeOsReleaseChannel policy is not specified then users of the enrolling domain will be allowed to change the release channel of the device. If this policy is set to false the device will be locked in whatever channel it was last set.
+      'desc': '''Users are only allowed to change the release channel of the device if this policy is set to True. If this policy is False or not set, users are not allowed to change the channel.
 
-      The user selected channel will be overridden by the ChromeOsReleaseChannel policy, but if the policy channel is more stable than the one that was installed on the device, then the channel will only switch after the version of the more stable channel reaches a higher version number than the one installed on the device.''',
+      Setting <ph name="CHROME_OS_RELEASE_CHANNEL_POLICY_NAME">ChromeOsReleaseChannel</ph> only has an effect if <ph name="CHROME_OS_RELEASE_CHANNEL_DELEGATED_POLICY_NAME">ChromeOsReleaseChannelDelegated</ph> is set to False.''',
     },
     {
       'name': 'DeviceReleaseLtsTag',