Add a feature flag for UMA storage dimensions population.

The Storage Dimensions data depends on a certain service to be present
in the image. Add a feature flag so it can be propagated from the login
manager based on USE flags in the system image.

BUG=b:151176984
TEST=build

Change-Id: I5dd0f9324904884a948b953e2c6154c98b57cef5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2371869Reviewed-by: Paul Moy <pmoy@chromium.org>
Reviewed-by: Oleh Lamzin <lamzin@google.com>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Daniil Lunev <dlunev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#802129}

chrome/common/chrome_features.cc

@@ -820,6 +820,10 @@ const base::Feature kWebUIDarkMode {
 };
 
 #if defined(OS_CHROMEOS)
+// Populates storage dimensions in UMA log if enabled. Requires diagnostics
+// package in the image.
+const base::Feature kUmaStorageDimensions{"UmaStorageDimensions",
+                                          base::FEATURE_DISABLED_BY_DEFAULT};
 // Allow a Wilco DTC (diagnostics and telemetry controller) on Chrome OS.
 // More info about the project may be found here:
 // https://docs.google.com/document/d/18Ijj8YlC8Q3EWRzLspIi2dGxg4vIBVe5sJgMPt9SWYo

chrome/common/chrome_features.h

@@ -551,6 +551,8 @@ extern const base::Feature kWebTimeLimits;
 COMPONENT_EXPORT(CHROME_FEATURES) extern const base::Feature kWebUIDarkMode;
 
 #if defined(OS_CHROMEOS)
+COMPONENT_EXPORT(CHROME_FEATURES)
+extern const base::Feature kUmaStorageDimensions;
 COMPONENT_EXPORT(CHROME_FEATURES) extern const base::Feature kWilcoDtc;
 #endif  // defined(OS_CHROMEOS)