Fix keyword search erroneously not triggering in two obscure cases:

chrome/browser/autocomplete/autocomplete_edit.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_AUTOCOMPLETE_AUTOCOMPLETE_EDIT_H_
 #define CHROME_BROWSER_AUTOCOMPLETE_AUTOCOMPLETE_EDIT_H_
 #pragma once
 
 #include "base/memory/scoped_ptr.h"
 #include "base/string16.h"
@@ skipping 301 matching lines @@
   //     or the currently selected keyword if |is_keyword_hint| is false (see
   //     comments on keyword_ and is_keyword_hint_).
   void OnPopupDataChanged(
       const string16& text,
       GURL* destination_for_temporary_text_change,
       const string16& keyword,
       bool is_keyword_hint);
 
   // Called by the OmniboxView after something changes, with details about what
   // state changes occured.  Updates internal state, updates the popup if
-  // necessary, and returns true if any significant changes occurred.
+  // necessary, and returns true if any significant changes occurred.  Note that
+  // |text_differs| may be set even if |old_text| == |new_text|, e.g. if we've
+  // just committed an IME composition.
+  //
   // If |allow_keyword_ui_change| is false then the change should not affect
   // keyword ui state, even if the text matches a keyword exactly. This value
   // may be false when the user is composing a text with an IME.
-  bool OnAfterPossibleChange(const string16& new_text,
+  bool OnAfterPossibleChange(const string16& old_text,
+                             const string16& new_text,
                              size_t selection_start,
                              size_t selection_end,
                              bool selection_differs,
                              bool text_differs,
                              bool just_deleted_text,
                              bool allow_keyword_ui_change);
 
   // Invoked when the popup is going to change its bounds to |bounds|.
   void PopupBoundsChangedTo(const gfx::Rect& bounds);
 
@@ skipping 68 matching lines @@
 
   // Returns the default match for the current text, as well as the alternate
   // nav URL, if |alternate_nav_url| is non-NULL and there is such a URL.
   void GetInfoForCurrentText(AutocompleteMatch* match,
                              GURL* alternate_nav_url) const;
 
   // Reverts the edit box from a temporary text back to the original user text.
   // If |revert_popup| is true then the popup will be reverted as well.
   void RevertTemporaryText(bool revert_popup);
 
-  // Accepts current keyword if the user only typed a space at the end of
-  // |new_user_text| comparing to the |old_user_text|.
+  // Accepts current keyword if the user just typed a space at the end of
+  // |new_text|.  This handles both of the following cases:
+  //   (assume "foo" is a keyword, | is the input caret, [] is selected text)
+  //   foo| -> foo |      (a space was appended to a keyword)
+  //   foo[bar] -> foo |  (a space replaced other text after a keyword)
   // Returns true if the current keyword is accepted.
-  bool MaybeAcceptKeywordBySpace(const string16& old_user_text,
-                                 const string16& new_user_text);
+  bool MaybeAcceptKeywordBySpace(const string16& new_text);
 
-  // Checks if |allow_exact_keyword_match_| should be set to true according to
-  // the old and new user text and the current caret position. It does not take
-  // other factors into account, e.g. if the view is ready to change the keyword
-  // ui or not. This is only for the case of inserting a space character in the
-  // middle of the text. See the comment of |allow_exact_keyword_match_| below.
-  bool ShouldAllowExactKeywordMatch(const string16& old_user_text,
-                                    const string16& new_user_text,
-                                    size_t caret_position);
+  // Checks whether the user inserted a space into |old_text| and by doing so
+  // created a |new_text| that looks like "<keyword> <search phrase>".
+  bool CreatedKeywordSearchByInsertingSpaceInMiddle(
+      const string16& old_text,
+      const string16& new_text,
+      size_t caret_position) const;
 
   // Tries to start an instant preview for |match|. Returns true if instant
   // processed the match.
   bool DoInstant(const AutocompleteMatch& match, string16* suggested_text);
 
   // Starts a prerender for the given |match|.
   void DoPrerender(const AutocompleteMatch& match);
 
   // Starts a DNS prefetch for the given |match|.
   void DoPreconnect(const AutocompleteMatch& match);
@@ skipping 101 matching lines @@
   mutable GURL paste_and_go_alternate_nav_url_;
 
   Profile* profile_;
 
   // This is needed as prior to accepting the current text the model is
   // reverted, which triggers resetting instant. We don't want to update instant
   // in this case, so we use the flag to determine if this is happening.
   bool in_revert_;
 
   // Indicates if the upcoming autocomplete search is allowed to be treated as
-  // an exact keyword match. If it's true then keyword mode will be triggered
-  // automatically if the input is "<keyword> <search string>". We only allow
-  // such trigger when:
-  // 1.A single space character is added at the end of a keyword, such as:
-  //   (assume "foo" is a keyword, | is the input caret)
-  //   foo| -> foo |
-  //   foo[bar] -> foo |  ([bar] indicates a selected text "bar")
-  // 2.A single space character is inserted after a keyword when the caret is
-  //   not at the end of the line, such as:
-  //   foo|bar -> foo |bar
-  //
-  // It has no effect if a keyword is already selected.
+  // an exact keyword match.  If this is true then keyword mode will be
+  // triggered automatically if the input is "<keyword> <search string>".  We
+  // allow this when CreatedKeywordSearchByInsertingSpaceInMiddle() is true.
+  // This has no effect if we're already in keyword mode.
   bool allow_exact_keyword_match_;
 
   // Last value of InstantCompleteBehavior supplied to |SetSuggestedText|.
   InstantCompleteBehavior instant_complete_behavior_;
 
   DISALLOW_COPY_AND_ASSIGN(AutocompleteEditModel);
 };
 
 #endif  // CHROME_BROWSER_AUTOCOMPLETE_AUTOCOMPLETE_EDIT_H_