Improve text inputs focusing behaviour

1. save page scale factor if it is greater than minimal legible/readable scale
2. normalize sizeRect on current page scale factor to be measurable with caret and textboxRect

R=aelias@chromium.org

Review URL: https://codereview.chromium.org/527003002

git-svn-id: svn://svn.chromium.org/blink/trunk@181508 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[DevTools] Check m_frontendPage in InspectorFrontendHost.

This is another speculative crash fix (previous one was r181045).

BUG=400483

Review URL: https://codereview.chromium.org/546633006

git-svn-id: svn://svn.chromium.org/blink/trunk@181509 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make SVGElement::removeEventListener() mirror its addEventListener()

Simplify the implementation by having it mirror the addEventListener() version.

Which means creating a correct protector and passing it inwards.

Review URL: https://codereview.chromium.org/547103002

git-svn-id: svn://svn.chromium.org/blink/trunk@181510 bbb929c8-8fbe-4397-9dbb-9b2b20218538