[Sampling profiler] Enable reporting by default

Reporting has been enabled at 100% server-side for ages. This flips the
client default so we can avoid sending the experiment state.

Change-Id: I2c88ce73fbf23c83e4572d9db3c72bbda28a8243
Reviewed-on: https://chromium-review.googlesource.com/c/1351379Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Mike Wittman <wittman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611181}

components/metrics/call_stack_profile_metrics_provider.cc

@@ -217,7 +217,7 @@ PendingProfiles::PendingProfiles() : collection_enabled_(true) {}
 // CallStackProfileMetricsProvider --------------------------------------------
 
 const base::Feature CallStackProfileMetricsProvider::kEnableReporting = {
-    "SamplingProfilerReporting", base::FEATURE_DISABLED_BY_DEFAULT};
+    "SamplingProfilerReporting", base::FEATURE_ENABLED_BY_DEFAULT};
 
 CallStackProfileMetricsProvider::CallStackProfileMetricsProvider() {}