[Icons NTP] Make largeIconUrl and fallbackIconUrl available for Local…

… NTP, behind flag.

This renders and injects the chrome-search://large-icon and
chrome-search://fallback-icon URLs for the local NTP, which (in upcoming
CL) uses the presence of these flags to decide whether to render icons
instead of thumbnails. The feature is hidden behind flag "IconNTP/Enabled".

BUG=467712

Review URL: https://codereview.chromium.org/1016793003

Cr-Commit-Position: refs/heads/master@{#321283}

chrome/renderer/searchbox/searchbox_extension.cc

@@ -6,6 +6,7 @@
 
 #include "base/i18n/rtl.h"
 #include "base/json/string_escape.h"
+#include "base/metrics/field_trial.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
@@ -61,6 +62,12 @@ base::string16 V8ValueToUTF16(v8::Handle<v8::Value> v) {
   return base::string16(reinterpret_cast<const base::char16*>(*s), s.length());
 }
 
+// Returns whether we should use large icons on NTP.
+bool IsIconNTPEnabled() {
+  return StartsWithASCII(base::FieldTrialList::FindFullName("IconNTP"),
+                         "Enabled", true);
+}
+
 // Converts string16 to V8 String.
 v8::Handle<v8::String> UTF16ToV8String(v8::Isolate* isolate,
                                        const base::string16& s) {
@@ -99,6 +106,27 @@ v8::Handle<v8::String> GenerateThumbnailURL(
           "chrome-search://thumb/%d/%d", render_view_id, most_visited_item_id));
 }
 
+v8::Handle<v8::String> GenerateLargeIconURL(
+    v8::Isolate* isolate,
+    int render_view_id,
+    InstantRestrictedID most_visited_item_id) {
+  const int kIconSize = 96;  // To support high DPI; on screen it's 48 dp.
+  return UTF8ToV8String(
+      isolate,
+      base::StringPrintf("chrome-search://large-icon/%d/%d/%d",
+                         kIconSize, render_view_id, most_visited_item_id));
+}
+
+v8::Handle<v8::String> GenerateFallbackIconURL(
+    v8::Isolate* isolate,
+    int render_view_id,
+    InstantRestrictedID most_visited_item_id) {
+  return UTF8ToV8String(
+      isolate,
+      base::StringPrintf("chrome-search://fallback-icon/,,,,1/%d/%d",
+                         render_view_id, most_visited_item_id));
+}
+
 // Populates a Javascript MostVisitedItem object from |mv_item|.
 // NOTE: Includes "url", "title" and "domain" which are private data, so should
 // not be returned to the Instant page. These should be erased before returning
@@ -136,6 +164,14 @@ v8::Handle<v8::Object> GenerateMostVisitedItem(
            v8::Int32::New(isolate, restricted_id));
   obj->Set(v8::String::NewFromUtf8(isolate, "thumbnailUrl"),
            GenerateThumbnailURL(isolate, render_view_id, restricted_id));
+  if (IsIconNTPEnabled()) {
+    // Update website http://www.chromium.org/embeddedsearch when we make this
+    // permanent.
+    obj->Set(v8::String::NewFromUtf8(isolate, "largeIconUrl"),
+             GenerateLargeIconURL(isolate, render_view_id, restricted_id));
+    obj->Set(v8::String::NewFromUtf8(isolate, "fallbackIconUrl"),
+             GenerateFallbackIconURL(isolate, render_view_id, restricted_id));
+  }
   obj->Set(v8::String::NewFromUtf8(isolate, "title"),
            UTF16ToV8String(isolate, title));
   obj->Set(v8::String::NewFromUtf8(isolate, "domain"),