[TTS] Fix a bug with literal tap search preloading

Fixes a bug that caused the SERP to show blank. This was actually
due to preloading when that was inappropriate (on a literal tap)
when the user had accepted the opt-in.

This CL fixes the logic to make sure we have a resolving gesture
before we prefetch - server access is gated on the resolve since
it's the primary server request. The Cl with the bug is
https://crrev.com/c/2557337.

BUG=1160041

Change-Id: Ida97ffb037022b039c5d843f770edd2907716836
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2597886
Auto-Submit: Donn Denman <donnd@chromium.org>
Commit-Queue: Theresa  <twellington@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Reviewed-by: Sinan Sahin <sinansahin@google.com>
Cr-Commit-Position: refs/heads/master@{#838694}

chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchManager.java

@@ -1057,7 +1057,7 @@ public class ContextualSearchManager
                 }
                 if (mSearchRequest != null
                         && (!mDidStartLoadingResolvedSearchRequest || mShouldLoadDelayedSearch)) {
-                    // mShouldLoadDelayedSearch is used in the long-press case to load content.
+                    // mShouldLoadDelayedSearch is used in the non-preloading case to load content.
                     // Since content is now created and destroyed for each request, was impossible
                     // to know if content was already loaded or recently needed to be; this is for
                     // the case where it needed to be.

chrome/android/java/src/org/chromium/chrome/browser/contextualsearch/ContextualSearchPolicy.java

@@ -142,10 +142,7 @@ class ContextualSearchPolicy {
 
         // We never preload unless we have sent page context (done through a Resolve request).
         // Only some gestures can resolve, and only when resolve privacy rules are met.
-        return (mSelectionController.getSelectionType() == SelectionType.TAP
-                       || mSelectionController.getSelectionType()
-                               == SelectionType.RESOLVING_LONG_PRESS)
-                && shouldPreviousGestureResolve();
+        return isResolvingGesture() && shouldPreviousGestureResolve();
     }
 
     /**