Change exponential bucketing for Media data use UKM.

Privacy doc: https://docs.google.com/document/d/133SsQTd3L5ryQaI-q1rZsh6EeTsE_HxDFlthjlXi4CU/edit?ts=5f3c1ca0#

Bug: 1117645
Change-Id: Ifc3229de5e19cc78269cd6e6c3ae2d4ae1f1c11c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2363693Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Michael Crouse <mcrouse@chromium.org>
Auto-Submit: Michael Crouse <mcrouse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#799316}

chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer.cc

@@ -604,10 +604,10 @@ void UkmPageLoadMetricsObserver::RecordTimingMetrics(
       ukm::GetExponentialBucketMin(js_max_decoded_bytes_, 10));
 
   builder.SetNet_ImageBytes(
-      ukm::GetExponentialBucketMin(image_total_bytes_, 1.3));
+      ukm::GetExponentialBucketMin(image_total_bytes_, 1.15));
   builder.SetNet_ImageSubframeBytes(
-      ukm::GetExponentialBucketMin(image_subframe_bytes_, 1.3));
-  builder.SetNet_MediaBytes(ukm::GetExponentialBucketMin(media_bytes_, 1.3));
+      ukm::GetExponentialBucketMin(image_subframe_bytes_, 1.15));
+  builder.SetNet_MediaBytes(ukm::GetExponentialBucketMin(media_bytes_, 1.15));
 
   if (main_frame_timing_)
     ReportMainResourceTimingMetrics(timing, &builder);

chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer_unittest.cc

@@ -1351,13 +1351,13 @@ TEST_F(UkmPageLoadMetricsObserverTest, ImageMediaSizeMetrics) {
     // 30 KB for all images, 20 KB for subframe images, and 50 KB for media.
     tester()->test_ukm_recorder().ExpectEntryMetric(
         kv.second.get(), "Net.ImageBytes",
-        ukm::GetExponentialBucketMin(30 * 1024, 1.3));
+        ukm::GetExponentialBucketMin(30 * 1024, 1.15));
     tester()->test_ukm_recorder().ExpectEntryMetric(
         kv.second.get(), "Net.ImageSubframeBytes",
-        ukm::GetExponentialBucketMin(20 * 1024, 1.3));
+        ukm::GetExponentialBucketMin(20 * 1024, 1.15));
     tester()->test_ukm_recorder().ExpectEntryMetric(
         kv.second.get(), "Net.MediaBytes",
-        ukm::GetExponentialBucketMin(50 * 1024, 1.3));
+        ukm::GetExponentialBucketMin(50 * 1024, 1.15));
   }
 }