[Favicon] Add new fallback icon rendering flow.

chrome/common/favicon/favicon_url_parser.cc

Index: chrome/common/favicon/favicon_url_parser.cc
diff --git a/chrome/common/favicon/favicon_url_parser.cc b/chrome/common/favicon/favicon_url_parser.cc
index 16d78af4e9f816f4b8984310c7bd4518c5fe9118..091a4371bcd950d316652ebcf71f052312241b02 100644
--- a/chrome/common/favicon/favicon_url_parser.cc
+++ b/chrome/common/favicon/favicon_url_parser.cc
@@ -15,6 +15,7 @@ namespace {
 // Parameters which can be used in chrome://favicon path. See file
 // "chrome/browser/ui/webui/favicon_source.h" for a description of
 // what each does.
+const char kFallbackParameter[] = "fallback/";
 const char kIconURLParameter[] = "iconurl/";
 const char kLargestParameter[] = "largest/";
 const char kOriginParameter[] = "origin/";
@@ -40,6 +41,7 @@ bool ParseFaviconPath(const std::string& path,
   parsed->size_in_dip = gfx::kFaviconSize;
   parsed->device_scale_factor = 1.0f;
   parsed->path_index = std::string::npos;
+  parsed->fallback_specs_builder.reset(nullptr);
 
   if (path.empty())
     return false;
@@ -92,28 +94,39 @@ bool ParseFaviconPath(const std::string& path,
     parsed_index = slash + 1;
   }
 
+  if (HasSubstringAt(path, parsed_index, kFallbackParameter)) {
+    parsed_index += strlen(kFallbackParameter);
+    size_t slash = path.find("/", parsed_index);
+    if (slash == std::string::npos)
+      return false;
+    std::string fallback_str = path.substr(parsed_index, slash - parsed_index);
+    parsed->fallback_specs_builder.reset(
+        new favicon_base::FallbackIconSpecsBuilder());
+    if (!parsed->fallback_specs_builder->Parse(fallback_str))
+      return false;  // Parse failed.
+    parsed_index = slash + 1;
+  }
+
   if (HasSubstringAt(path, parsed_index, kIconURLParameter)) {
     parsed_index += strlen(kIconURLParameter);
     parsed->is_icon_url = true;
     parsed->url = path.substr(parsed_index);
-  } else {
+  } else if (HasSubstringAt(path, parsed_index, kOriginParameter)) {
     // URL requests prefixed with "origin/" are converted to a form with an
     // empty path and a valid scheme. (e.g., example.com -->
     // http://example.com/ or http://example.com/a --> http://example.com/)
-    if (HasSubstringAt(path, parsed_index, kOriginParameter)) {
-      parsed_index += strlen(kOriginParameter);
-      std::string possibly_invalid_url = path.substr(parsed_index);
+    parsed_index += strlen(kOriginParameter);
+    std::string possibly_invalid_url = path.substr(parsed_index);
 
-      // If the URL does not specify a scheme (e.g., example.com instead of
-      // http://example.com), add "http://" as a default.
-      if (!GURL(possibly_invalid_url).has_scheme())
-        possibly_invalid_url = "http://" + possibly_invalid_url;
+    // If the URL does not specify a scheme (e.g., example.com instead of
+    // http://example.com), add "http://" as a default.
+    if (!GURL(possibly_invalid_url).has_scheme())
+      possibly_invalid_url = "http://" + possibly_invalid_url;
 
-      // Strip the path beyond the top-level domain.
-      parsed->url = GURL(possibly_invalid_url).GetOrigin().spec();
-    } else {
-      parsed->url = path.substr(parsed_index);
-    }
+    // Strip the path beyond the top-level domain.
+    parsed->url = GURL(possibly_invalid_url).GetOrigin().spec();
+  } else {
+    parsed->url = path.substr(parsed_index);
   }
 
   // The parsed index needs to be returned in order to allow Instant Extended