Add UMA histogram for the scheme of a developer resource load

Drive-by: Fix formatting issue in "DevTools.DeveloperResourceLoaded"
Front-end CL: https://crrev.com/c/2637697

Bug: chromium:1069378
Change-Id: I826655852ac19660855716407e75e13440869d3e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2637514Reviewed-by: Jesse Doherty <jwd@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845094}

chrome/browser/devtools/devtools_ui_bindings.cc

@@ -142,6 +142,8 @@ static const char kDevToolsCssEditorOpenedHistogram[] =
 static const char kDevToolsIssueCreatedHistogram[] = "DevTools.IssueCreated";
 static const char kDevToolsDeveloperResourceLoadedHistogram[] =
     "DevTools.DeveloperResourceLoaded";
+static const char kDevToolsDeveloperResourceSchemeHistogram[] =
+    "DevTools.DeveloperResourceScheme";
 
 static const char kRemotePageActionInspect[] = "inspect";
 static const char kRemotePageActionReload[] = "reload";
@@ -1318,7 +1320,8 @@ void DevToolsUIBindings::RecordEnumeratedHistogram(const std::string& name,
       name == kDevToolsGridOverlayOpenedFromHistogram ||
       name == kDevToolsCssEditorOpenedHistogram ||
       name == kDevToolsIssueCreatedHistogram ||
-      name == kDevToolsDeveloperResourceLoadedHistogram)
+      name == kDevToolsDeveloperResourceLoadedHistogram ||
+      name == kDevToolsDeveloperResourceSchemeHistogram)
     base::UmaHistogramExactLinear(name, sample, boundary_value);
   else
     frontend_host_->BadMessageReceived();

tools/metrics/histograms/enums.xml

@@ -17158,6 +17158,18 @@ metrics consent we also won't be able to send UMA metrics. -->
   <int value="7" label="FallbackFailure"/>
 </enum>
 
+<enum name="DevToolsDeveloperResourceScheme">
+  <int value="0" label="SchemeOther"/>
+  <int value="1" label="SchemeUnknown"/>
+  <int value="2" label="SchemeHttp"/>
+  <int value="3" label="SchemeHttps"/>
+  <int value="4" label="SchemeHttpLocalhost"/>
+  <int value="5" label="SchemeHttpsLocalhost"/>
+  <int value="6" label="SchemeData"/>
+  <int value="7" label="SchemeFile"/>
+  <int value="8" label="SchemeBlob"/>
+</enum>
+
 <enum name="DevToolsDualScreenDeviceEmulated">
   <int value="0" label="Dual-screen or fold device selected"/>
   <int value="1" label="Dual-screen span mode selected"/>

tools/metrics/histograms/histograms_xml/dev/histograms.xml

@@ -139,6 +139,7 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
     Some explanations to make sense of the enum values:
 
     LoadsThroughPage = LoadThroughPageViaTarget + LoadThroughPageViaFrame
+
     SuccessfulLoadsThroughPage = LoadsThroughPage - LoadThroughPageFailure
 
     LoadThroughPageFallback is the number of loads that can in principle be
@@ -160,6 +161,24 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
   </summary>
 </histogram>
 
+<histogram name="DevTools.DeveloperResourceScheme"
+    enum="DevToolsDeveloperResourceScheme" expires_after="2021-12-31">
+  <owner>yangguo@chromium.org</owner>
+  <owner>sigurds@chromium.org</owner>
+  <summary>
+    Records for each developer resource load that the DevTools front-end issues
+    (e.g. to load a source map) one enum value that records the scheme of the
+    resource's URL. For HTTP and HTTPS schemes, there are two enums each: One
+    that signifies that the host was localhost, and one that signifies that it
+    wasn't, i.e. to get the total number of resource loads using a HTTP scheme
+    one must add the numbers of SchemeHttp and SchemeHttpLocalhost.
+
+    The value SchemeUnknown signifies that parsing the scheme from the URL
+    failed (note that at the point the enum is recorded, only absolute URLs
+    arrive).
+  </summary>
+</histogram>
+
 <histogram name="DevTools.DualScreenDeviceEmulated"
     enum="DevToolsDualScreenDeviceEmulated" expires_after="M87">
   <owner>yangguo@chromium.org</owner>