Omnibox: Suggestion Transparency - Add 'Why this Suggestion' text.

This extends AutocompleteMatch with explanatory text as to where this
suggestion came from. This is currently purely based on the
AutocompleteMatchType.

These are placeholder strings meant for development only.

Bug: 929477
Change-Id: Ia8bb271b6f7ad4b2848011bec98d16d4f64f64de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1574886
Commit-Queue: Tommy Li <tommycli@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652865}

components/omnibox/browser/autocomplete_match.cc

@@ -292,6 +292,93 @@ const gfx::VectorIcon& AutocompleteMatch::GetVectorIcon(
 }
 #endif
 
+base::string16 AutocompleteMatch::GetWhyThisSuggestionText() const {
+  // TODO(tommycli): Replace these placeholder strings with final ones from UX.
+  switch (type) {
+    case Type::URL_WHAT_YOU_TYPED:
+      return base::ASCIIToUTF16(
+          "This navigation match is the exact URL you typed.");
+
+    case Type::HISTORY_URL:
+    case Type::HISTORY_TITLE:
+    case Type::HISTORY_BODY:
+    case Type::HISTORY_KEYWORD:
+      return base::ASCIIToUTF16(
+          "This navigation match is a previously visited page from Chrome "
+          "History.");
+
+    case Type::NAVSUGGEST:
+      return base::ASCIIToUTF16(
+          "This navigation match is suggested by the search engine based on "
+          "what you typed.");
+
+    case Type::SEARCH_WHAT_YOU_TYPED:
+      return base::ASCIIToUTF16("This search query is exactly what you typed.");
+
+    case Type::SEARCH_HISTORY:
+      // TODO(tommycli): We may need to distinguish between matches sourced
+      // from search history saved in the cloud vs. locally.
+      return base::ASCIIToUTF16(
+          "This search query is suggested by the search engine based on what "
+          "you typed and past search queries.");
+
+    case Type::SEARCH_SUGGEST:
+    case Type::SEARCH_SUGGEST_ENTITY:
+    case Type::SEARCH_SUGGEST_TAIL:
+      return base::ASCIIToUTF16(
+          "This search query is suggested by the search engine based on what "
+          "you typed.");
+
+    case Type::SEARCH_SUGGEST_PERSONALIZED:
+      return base::ASCIIToUTF16(
+          "This search query is suggested by the search engine based on what "
+          "you typed. It has also been personalized to you.");
+
+    case Type::SEARCH_OTHER_ENGINE:
+      return base::ASCIIToUTF16(
+          "This search query is for a non-default search engine.");
+
+    case Type::BOOKMARK_TITLE:
+      return base::ASCIIToUTF16(
+          "This navigation matches the title of a Bookmark.");
+
+    case Type::NAVSUGGEST_PERSONALIZED:
+      return base::ASCIIToUTF16(
+          "This navigation match is suggested by the search engine based on "
+          "what you typed. It has also been personalized to you.");
+
+    case Type::CALCULATOR:
+      return base::ASCIIToUTF16(
+          "This calculation is the result of evaluating your input provided by "
+          "your default search engine.");
+
+    case Type::CLIPBOARD_URL:
+    case Type::CLIPBOARD_TEXT:
+    case Type::CLIPBOARD_IMAGE:
+      return base::ASCIIToUTF16("This match is from the system clipboard.");
+
+    case Type::VOICE_SUGGEST:
+      return base::ASCIIToUTF16("This match is from voice.");
+
+    case Type::DOCUMENT_SUGGESTION:
+      return base::ASCIIToUTF16("This match is from your documents.");
+
+    case Type::PEDAL:
+      return base::ASCIIToUTF16(
+          "This is a suggested Chrome action based on what you typed.");
+
+    case Type::EXTENSION_APP_DEPRECATED:
+    case Type::SEARCH_SUGGEST_PROFILE:
+    case Type::CONTACT_DEPRECATED:
+    case Type::PHYSICAL_WEB_DEPRECATED:
+    case Type::PHYSICAL_WEB_OVERFLOW_DEPRECATED:
+    case Type::TAB_SEARCH_DEPRECATED:
+    case Type::NUM_TYPES:
+      NOTREACHED();
+      return base::string16();
+  }
+}
+
 // static
 bool AutocompleteMatch::MoreRelevant(const AutocompleteMatch& elem1,
                                      const AutocompleteMatch& elem2) {

components/omnibox/browser/autocomplete_match.h

@@ -156,6 +156,10 @@ struct AutocompleteMatch {
   const gfx::VectorIcon& GetVectorIcon(bool is_bookmark) const;
 #endif
 
+  // Returns text explaining why this suggestion was displayed. Can return an
+  // empty string if there is no explanation.
+  base::string16 GetWhyThisSuggestionText() const;
+
   // Comparison function for determining when one match is better than another.
   static bool MoreRelevant(const AutocompleteMatch& elem1,
                            const AutocompleteMatch& elem2);