[Search] Make the feature name link to a learn more screen in the first-run experience.

Updated wording as well.

BUG=413337
TEST=manual

Review URL: https://codereview.chromium.org/597673003

Cr-Commit-Position: refs/heads/master@{#296441}

chrome/app/chromium_strings.grd

@@ -1205,8 +1205,14 @@ Signing in anyway will merge Chromium information like bookmarks, history, and o
       <message name="IDS_CONTEXTUAL_SEARCH_HEADER" desc="Header shown at the top of the first run experience, to describe the Contextual Search feature.">
         Search with one touch
       </message>
-      <message name="IDS_CONTEXTUAL_SEARCH_PROMO_DESCRIPTION" desc="Description of the Contextual Search feature.">
-        Using “Touch to Search” you can touch any word on a website to learn more about a topic. Chromium will send that word and the surrounding contents to Google and bring back relevant information about it.
+      <message name="IDS_CONTEXTUAL_SEARCH_PROMO_DESCRIPTION_1" desc="Part 1 of the description of the Contextual Search feature. Combined with FEATURE_NAME and DESCRIPTION_2 below, the whole should be a paragraph describing the feature. This line can be empty if it makes sense to start the sentence with FEATURE_NAME.">
+        Learn about topics on websites without leaving your browser.
+      </message>
+      <message name="IDS_CONTEXTUAL_SEARCH_PROMO_FEATURE_NAME" desc="Name of the Contextual Search feature. See explanation in DESCRIPTION_1.">
+        Tap to Search
+      </message>
+      <message name="IDS_CONTEXTUAL_SEARCH_PROMO_DESCRIPTION_2" desc="Part 2 of the description of the Contextual Search feature. See explanation in DESCRIPTION_1.">
+        sends a word and its surrounding context to Google Search, returning definitions, pictures, search results, and other details.
       </message>
       <message name="IDS_CONTEXTUAL_SEARCH_PROMO_OPTIN" desc="Text for the button the user clicks to opt in.">
         Accept &amp; Search

chrome/app/google_chrome_strings.grd

@@ -1130,8 +1130,14 @@ Signing in anyway will merge Chrome information like bookmarks, history, and oth
       <message name="IDS_CONTEXTUAL_SEARCH_HEADER" desc="Header shown at the top of the first run experience, to describe the Contextual Search feature.">
         Search with one touch
       </message>
-      <message name="IDS_CONTEXTUAL_SEARCH_PROMO_DESCRIPTION" desc="Description of the Contextual Search feature.">
-        Using “Touch to Search” you can touch any word on a website to learn more about a topic. Chrome will send that word and the surrounding contents to Google and bring back relevant information about it.
+      <message name="IDS_CONTEXTUAL_SEARCH_PROMO_DESCRIPTION_1" desc="Part 1 of the description of the Contextual Search feature. Combined with FEATURE_NAME and DESCRIPTION_2 below, the whole should be a paragraph describing the feature. This line can be empty if it makes sense to start the sentence with FEATURE_NAME.">
+        Learn about topics on websites without leaving your browser.
+      </message>
+      <message name="IDS_CONTEXTUAL_SEARCH_PROMO_FEATURE_NAME" desc="Name of the Contextual Search feature. See explanation in DESCRIPTION_1.">
+        Tap to Search
+      </message>
+      <message name="IDS_CONTEXTUAL_SEARCH_PROMO_DESCRIPTION_2" desc="Part 2 of the description of the Contextual Search feature. See explanation in DESCRIPTION_1.">
+        sends a word and its surrounding context to Google Search, returning definitions, pictures, search results, and other details.
       </message>
       <message name="IDS_CONTEXTUAL_SEARCH_PROMO_OPTIN" desc="Text for the button the user clicks to opt in.">
         Accept &amp; Search

chrome/browser/resources/contextual_search/promo.css

@@ -17,6 +17,7 @@ body {
 
 a {
   color: #414141;
+  text-decoration: none;
 }
 
 .colored {
@@ -32,7 +33,6 @@ a {
 }
 
 .label a {
-  text-decoration: none;
   text-transform: uppercase;
 }
 

chrome/browser/resources/contextual_search/promo.html

@@ -15,7 +15,11 @@
   <div id="container">
     <img id="header-image" src="header.svg">
     <p i18n-content="heading" id="heading"></p>
-    <p i18n-content="description" id="description"></p>
+    <p id="description">
+      <span i18n-content="description-1"></span>
+      <a class="colored" href="#learn-more" i18n-content="feature-name"></a>
+      <span i18n-content="description-2"></span>
+    </p>
     <div id="button-container">
       <span class="label"><a href="#optout" i18n-content="optOut"></a></span>
       <span id="optin-label" class="label"><a class="colored" href="#optin" i18n-content="optIn"></a></span>

chrome/browser/search/contextual_search_promo_source_android.cc

@@ -130,9 +130,17 @@ void ContextualSearchPromoSourceAndroid::SendConfigResource(
 void ContextualSearchPromoSourceAndroid::SendHtmlWithStrings(
     const content::URLDataSource::GotDataCallback& callback) {
   base::DictionaryValue strings_data;
+  // The three following statements are part of the description paragraph.
   strings_data.SetString(
-      "description",
-      l10n_util::GetStringUTF16(IDS_CONTEXTUAL_SEARCH_PROMO_DESCRIPTION));
+      "description-1",
+      l10n_util::GetStringUTF16(IDS_CONTEXTUAL_SEARCH_PROMO_DESCRIPTION_1));
+  strings_data.SetString(
+      "feature-name",
+      l10n_util::GetStringUTF16(IDS_CONTEXTUAL_SEARCH_PROMO_FEATURE_NAME));
+  strings_data.SetString(
+      "description-2",
+      l10n_util::GetStringUTF16(IDS_CONTEXTUAL_SEARCH_PROMO_DESCRIPTION_2));
+
   strings_data.SetString(
       "heading", l10n_util::GetStringUTF16(IDS_CONTEXTUAL_SEARCH_HEADER));
   strings_data.SetString(