[iOS CBCM] Enable CBCM at 100% on Beta

Enables CBCM at 100% on Beta on iOS (in addition to the existing
command-line switch, which can enable CBCM in any channel). To
paraphrase the comment in the code, CBCM must either be enabled
at 100% or 0% because the Finch infrastructure isn't ready by the
time CBCM must decide whether to initialize.

Because of additional requirements explained in the following 1-pager
(Google only), CBCM is required on Beta, which means CBCM will be
enabled at 100% on Beta and 0% on all other channels:
go/ios-cbcm-rollout-1pager.

Bug: 1066495
Change-Id: I1449f5314ea592297d79ec7acbbb0991d31bed5a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2364912
Commit-Queue: Guillaume Jenkins <gujen@google.com>
Reviewed-by: sebsg <sebsg@chromium.org>
Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#800330}

ios/chrome/browser/policy/policy_features.cc

@@ -41,7 +41,16 @@ bool IsDisableEnterprisePolicySwitchPresent() {
 }  // namespace
 
 bool IsChromeBrowserCloudManagementEnabled() {
-  return HasSwitch(switches::kEnableChromeBrowserCloudManagement);
+  // This method is called very early during the launch sequence (inside
+  // IOSChromeMainParts::PreCreateThreads). At that point, the FeatureList API
+  // isn't ready yet, so neither Finch experiments nor first-run field trials
+  // can be used for progressive rollout. To ensure adequate coverage of both
+  // the "CBCM disabled" and "CBCM enabled" code paths, CBCM is enabled at 100%
+  // on Beta and 0% on all other channels (CBCM is disabled by default). This
+  // allows monitoring crashes for both code paths while allowing early adopters
+  // to use CBCM on the Beta channel.
+  return HasSwitch(switches::kEnableChromeBrowserCloudManagement) ||
+         GetChannel() == version_info::Channel::BETA;
 }
 
 bool IsEditBookmarksIOSEnabled() {