ContentCapture: User activated delay

- Sets UserActivation if the proper user input occurred.
- Schedules the shortest delay task if any change happened within a
  active UserActivation.
- Otherwise, applies exponential delay up to 128s.
- Guarded with feature for finch experiment.

Bug: 1114819
Change-Id: I4580a1168f0b06706f9b5837074263a03254fee8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2349402
Reviewed-by: Xianzhu Wang <[email protected]>
Reviewed-by: Philip Rogers <[email protected]>
Reviewed-by: Alexei Svitkine <[email protected]>
Reviewed-by: John Abd-El-Malek <[email protected]>
Commit-Queue: Tao Bai <[email protected]>
Cr-Commit-Position: refs/heads/master@{#798987}
diff --git a/third_party/blink/common/features.cc b/third_party/blink/common/features.cc
index db67cf7b..e319b4f 100644
--- a/third_party/blink/common/features.cc
+++ b/third_party/blink/common/features.cc
@@ -699,5 +699,9 @@
 const base::Feature kReducedReferrerGranularity{
     "ReducedReferrerGranularity", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables the user activated exponential delay in the ContentCapture task.
+const base::Feature kContentCaptureUserActivatedDelay = {
+    "ContentCaptureUserActivatedDelay", base::FEATURE_DISABLED_BY_DEFAULT};
+
 }  // namespace features
 }  // namespace blink