[Autofill/Autocomplete Feature] Substring matching instead of prefix matching.

components/autofill/content/renderer/form_autofill_util.h

Index: components/autofill/content/renderer/form_autofill_util.h
diff --git a/components/autofill/content/renderer/form_autofill_util.h b/components/autofill/content/renderer/form_autofill_util.h
index 1be05cdac08433fab3baf5dd2e293ea3d2af413c..708b30b8b3a75fda2878d1e769de623465b0b55c 100644
--- a/components/autofill/content/renderer/form_autofill_util.h
+++ b/components/autofill/content/renderer/form_autofill_util.h
@@ -176,6 +176,28 @@ bool IsWebElementEmpty(const blink::WebElement& element);
 // Return a gfx::RectF that is the bounding box for |element| scaled by |scale|.
 gfx::RectF GetScaledBoundingBox(float scale, blink::WebElement* element);
 
+// Previews the |input_element| with supplied |suggestion| text and highlights

[vabr (Chromium), 2015/07/13 14:04:25]

grammar: missing definite articles:
the |suggestion| text
the |input_element| text
the end of the |suggestion| text

[vabr (Chromium), 2015/07/13 14:04:25]

Sorry, I gave up listing the nits for this comment block, and instead supply my
own version. Please observe the following objectives when writing comments:
* use simple, clear sentences
* don't create large blocks of repeated text, nobody will be able to read those
* first define what things are, then speak about them, not the other way round
* for complicated cases, consider using examples
* nouns need almost always articles in front of them; a particular exception are
names, including variable names (e.g., "|suggestion|", but "a/the |suggestion|
text")

My suggestion for the comment (note, that I intentionally left out the
discussion of substrings, because it is not essential to understand the main job
of this function):

Previews |suggestion| in |input_element| and highlights the suffix of
|suggestion| not included in the |input_element| text. |input_element| must not
be null. |user_input| should be the text typed by the user into |input_element|.
Note that |user_input| cannot be easily derived from |input_element| by calling
value(), because of http://crbug.com/507714.

[vabr (Chromium), 2015/07/13 14:04:26]

Wrong valency for preview, please change to:
Previews |suggestion| in |input_element| and highlights...

[Pritam Nikam, 2015/07/14 10:30:07]

Done.

Thanks. Above points you mentioned will definitely help me to improve drafting
comments. I'll take care in future.

+// the part of |input_element| text from the end of the |user_input| text till
+// end of |suggestion| text.
+// The |input_element| is the text field being considered for preview and should

[vabr (Chromium), 2015/07/13 14:04:26]

nit: Do not repeat that the preview is done in the input element, just say that
it should not be null.

+// not be null.
+// The |suggestion| text is the field's suggestion to be previewed in the

[vabr (Chromium), 2015/07/13 14:04:26]

This sentence is completely duplicating what has already been said.

+// |input_element| and being highlighted.
+// And the |user_input| text is the field contents that user has typed.
+// If the |user_input| text prefixes the |suggestion|, the |input_element|'s
+// text selection range starts at |user_input|'s string length till the
+// |suggestion| string's end. If |kEnableSuggestionsWithSubstringMatch| commond
+// line switch is enabled and the |user_input| substrings the field's
+// |suggestion| starting at token boundaries, the text selection range starts at
+// part of the |suggestion| string where |user_input| string ends till the
+// |suggestion| string's end.
+// Here, we are not using input_element->value() and
+// input_element->suggestedValue() directly because password manager sometimes
+// does not set them. http://crbug.com/507714
+void PreviewSuggestion(const base::string16& suggestion,
+                       const base::string16& user_input,
+                       blink::WebFormControlElement* input_element);
+
 }  // namespace autofill
 
 #endif  // COMPONENTS_AUTOFILL_CONTENT_RENDERER_FORM_AUTOFILL_UTIL_H_