Cleanup: Fix typos in page_load_metrics/observers/ad_metrics files.

Change-Id: I14c30dd135dc2f4fe813c4cee927ba911d33f28e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2305672Reviewed-by: Josh Karlin <jkarlin@chromium.org>
Commit-Queue: Cammie Smith Barnes <cammie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795666}

chrome/browser/page_load_metrics/observers/ad_metrics/ads_page_load_metrics_observer.cc

@@ -54,7 +54,7 @@
 
 namespace features {
 
-// Enables of disabled the restricted navigation ad tagging feature. When
+// Enables or disables the restricted navigation ad tagging feature. When
 // enabled, the AdTagging heuristic is modified to additional information to
 // determine if a frame is an ad. If the frame's navigation url matches an allow
 // list rule, it is not an ad.

chrome/browser/page_load_metrics/observers/ad_metrics/ads_page_load_metrics_observer.h

@@ -250,7 +250,7 @@ class AdsPageLoadMetricsObserver
                  subresource_filter::SubresourceFilterObserver>
       subresource_observer_;
 
-  // The tick clock used to get the current time.  Can be replaced by tests.
+  // The tick clock used to get the current time. Can be replaced by tests.
   const base::TickClock* clock_;
 
   // Whether the page load currently being observed is a reload of a previous
@@ -280,7 +280,7 @@ class AdsPageLoadMetricsObserver
   std::unique_ptr<HeavyAdThresholdNoiseProvider>
       heavy_ad_threshold_noise_provider_;
 
-  // The maximum ad density measurements for the page during it's lifecycle.
+  // The maximum ad density measurements for the page during its lifecycle.
   PageAdDensityTracker page_ad_density_tracker_;
 
   DISALLOW_COPY_AND_ASSIGN(AdsPageLoadMetricsObserver);

chrome/browser/page_load_metrics/observers/ad_metrics/frame_data.cc

@@ -316,7 +316,7 @@ void FrameData::SetFirstEligibleToPaint(
     // If the ad frame tree hasn't already received an earlier paint
     // eligibility stamp, mark it as eligible to paint. Since multiple frames
     // may report timestamps, we keep the earliest reported stamp.
-    // Note that this timestamp (or lack tereof) is best-effort.
+    // Note that this timestamp (or lack thereof) is best-effort.
     if (!first_eligible_to_paint_.has_value() ||
         first_eligible_to_paint_.value() > time_stamp.value())
       first_eligible_to_paint_ = time_stamp;