[On-device adaptive brightness] Add a flag to control auto screen brightness model.

Bug: 881215
Test: unit_tests --gtest_filter=AboutFlagsTest*, AboutFlagsHistogramTest*
Change-Id: Ia1749065e2b41bba2f402d7790e9e00d7592b144
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1610666
Commit-Queue: Jia Meng <[email protected]>
Reviewed-by: Andrew Moylan <[email protected]>
Cr-Commit-Position: refs/heads/master@{#659748}
diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
index cd585d3..a3a28de 100644
--- a/chrome/browser/flag_descriptions.cc
+++ b/chrome/browser/flag_descriptions.cc
@@ -206,6 +206,11 @@
     "When enabled, the Autofill dropdown's suggestions' labels are displayed "
     "using the improved disambiguation format.";
 
+const char kAutoScreenBrightnessName[] = "Auto Screen Brightness model";
+const char kAutoScreenBrightnessDescription[] =
+    "Uses Auto Screen Brightness model to adjust screen brightness based on "
+    "ambient light";
+
 const char kAwaitOptimizationName[] = "Await optimization";
 const char kAwaitOptimizationDescription[] =
     "Enables await taking 1 tick on the microtask queue.";