[flutter_tools][web] add favicon to template and update index.html (#49237)

dev/bots/analyze.dart

@@ -824,6 +824,10 @@ final Set<Hash256> _grandfatheredBinaries = <Hash256>{
   // examples/flutter_gallery/web/icons/Icon-512.png
   Hash256(0xBACCB205AE45f0B4, 0x21BE1657259B4943, 0xAC40C95094AB877F, 0x3BCBE12CD544DCBE),
 
+  // packages/flutter_tools/templates/app/web/favicon.png.copy.tmpl
+  // examples/flutter_gallery/web/favicon.png
+  Hash256(0x7AB2525F4B86B65D, 0x3E4C70358A17E5A1, 0xAAF6F437f99CBCC0, 0x46DAD73d59BB9015),
+
   // GALLERY ICONS
 
   // examples/flutter_gallery/android/app/src/main/res/mipmap-hdpi/ic_background.png
@@ -1056,7 +1060,7 @@ Future<void> verifyNoBinaries(String workingDirectory, { Set<Hash256> grandfathe
   assert(
     _grandfatheredBinaries
       .expand<int>((Hash256 hash) => <int>[hash.a, hash.b, hash.c, hash.d])
-      .reduce((int value, int element) => value ^ element) == 0xBFC18DE113B5AE8E // Please do not modify this line.
+      .reduce((int value, int element) => value ^ element) == 0x17138C817203D1A7 // Please do not modify this line.
   );
   grandfatheredBinaries ??= _grandfatheredBinaries;
   if (!Platform.isWindows) { // TODO(ianh): Port this to Windows

examples/flutter_gallery/web/index.html

@@ -13,6 +13,7 @@ found in the LICENSE file. -->
   <meta name="apple-mobile-web-status-bar-style" content="black">
   <meta name="apple-mobile-web-app-title" content="Flutter Gallery">
   <link rel="apple-touch-icon" href="/icons/Icon-192.png">
+  <link rel="shortcut icon" type="image/png" href="/favicon.png"/>
 
   <title>Flutter Gallery</title>
   <link rel="manifest" href="/manifest.json">

packages/flutter_tools/templates/app/web/index.html.tmpl

@@ -11,6 +11,9 @@
   <meta name="apple-mobile-web-app-title" content="{{projectName}}">
   <link rel="apple-touch-icon" href="/icons/Icon-192.png">
 
+  <!-- Favicon -->
+  <link rel="shortcut icon" type="image/png" href="/favicon.png"/>
+
   <title>{{projectName}}</title>
   <link rel="manifest" href="/manifest.json">
 </head>