Fix a crash by AdvanceToNextMisspelling command (⌘-;) with empty INPUT

third_party/WebKit/Source/core/css/html.css

Index: third_party/WebKit/Source/core/css/html.css
diff --git a/third_party/WebKit/Source/core/css/html.css b/third_party/WebKit/Source/core/css/html.css
index 9b6161af2510587ee121e9c0b900538db1378156..cc3587c2d3d4bd70f587dab3e098bb2f852d0a0c 100644
--- a/third_party/WebKit/Source/core/css/html.css
+++ b/third_party/WebKit/Source/core/css/html.css
@@ -530,6 +530,7 @@ textarea {
     -webkit-text-security: none;
     color: darkGray;
     pointer-events: none !important;
+    -webkit-user-select: none;

[yosin_UTC9, 2016/02/09 05:06:13]

It is strange that we attempt to spell check "read-only" text,
input::-webkit-input-placeholder selector sets so.
We should fix |advanceToNextMisspelling()| not to attempt checking spell for
"read-only" text rather than make placeholder unselectable to make user created
INPUT element not to crash.

[tkent, 2016/02/09 05:09:26]

I see. So, the following code in SpellChecker::advanceToNextMisspelling()
doesn't check editability.  I'll investigate it.

    // If spellingSearchRange starts in the middle of a word, advance to the
    // next word so we start checking at a word boundary. Going back by one char
    // and then forward by a word does the trick.
    if (startedWithSelection) {
    VisiblePosition oneBeforeStart =
previousPositionOf(createVisiblePosition(spellingSearchStart));
        if (oneBeforeStart.isNotNull())
            spellingSearchStart =
endOfWord(oneBeforeStart).toParentAnchoredPosition();
        // else we were already at the start of the editable node
    }

 }
 
 input::-webkit-input-placeholder {