Add back buttons and load new 'pages' by calling javascript.

build/android/pylib/results/presentation/javascript/main_html.js

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 function getArguments() {
   // Returns the URL arguments as a dictionary.
   args = {}
   var s = location.search;
   if (s) {
     var vals = s.substring(1).split('&');
@@ skipping 28 matching lines @@
             .startsWith(suite_name);
           if (!table_block_in_suite) {
             testTableBlock.style.display = 'none';
             return;
           }
         }
         testTableBlock.style.display = 'table-row-group';
       });
   showTestTable(true);
   showSuiteTable(false);
+  window.scrollTo(0, 0);
+}
+
+function showTestsOfOneSuiteOnlyWithNewState(suite_name) {
+  showTestsOfOneSuiteOnly(suite_name);
+  history.pushState({suite: suite_name}, suite_name, '');
 }
 
 function showSuiteTableOnly() {
   setTitle('Suites Summary')
   showTestTable(false);
   showSuiteTable(true);
+  window.scrollTo(0, 0);
+}
+
+function showSuiteTableOnlyWithReplaceState() {
+  showSuiteTableOnly();
+  history.replaceState({}, 'suite_table', '');
+}
+
+function setBrowserBackButtonLogic() {
+  window.onpopstate = function(event) {
+    if (!event.state || !event.state.suite) {
+      showSuiteTableOnly();
+    } else {
+      showTestsOfOneSuiteOnly(event.state.suite);
+    }
+  };
 }
 
 function setTitle(title) {
   document.getElementById('summary-header').textContent = title;
 }
 
 function sortByColumn(head) {
   var table = head.parentNode.parentNode.parentNode;
   var rowBlocks = Array.prototype.slice.call(
       table.getElementsByTagName('tbody'));
@@ skipping 94 matching lines @@
           (b_rows.length - b_success_or_skipped) / btotal_minus_skipped);
     }
     return asc * (avalue - bvalue);
   });
 
   for (var i = 0; i < rowBlocks.length; i++) {
     table.appendChild(rowBlocks[i]);
   }
 }
 
-function loadPage() {
-  var args = getArguments();
-  if ('suite' in args) {
-    // The user wants to visit detailed 'subpage' of that suite.
-    showTestsOfOneSuiteOnly(args['suite']);
-  } else {
-    // The user wants to visit the summary of all suites.
-    showSuiteTableOnly();
-  }
-}
-
 function reportIssues() {
   var url = 'https://bugs.chromium.org/p/chromium/issues/entry?' +
             'labels=Pri-2,Type-Bug,Restrict-View-Google&' +
             'summary=Result Details Feedback:&' +
             'comment=Please check out: ' + window.location;
   var newWindow = window.open(url, '_blank');
   newWindow.focus();
 }