Multi-column properties in a flexbox hide its content

In a flexbox if you set any of the multi-column properties (column-*)
the content of the flexbox is hidden.

According to the spec http://www.w3.org/TR/css3-flexbox/#propdef-flex
muti-column properties should be ignored:

"all of the column-* properties in the Multicol module have no
effect on a flex container."

This patch fixes this bug by adding a check in RenderBlock::requiresColumns
that columns are not required for Flexible box.

BUG=402124

Review URL: https://codereview.chromium.org/488183003

git-svn-id: svn://svn.chromium.org/blink/trunk@180776 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Use hb_direction_t in HarfBuzzShaper::HarfBuzzRun

Change HarfBuzzShaper to use hb_direction_t instead of TextDirection in
HarfBuzzRun and run cache to avoid unnecessary type conversions.

R=pdr@chromium.org

Review URL: https://codereview.chromium.org/498543003

git-svn-id: svn://svn.chromium.org/blink/trunk@180777 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Touch adjustment: don't treat iframes as clickable by default

Iframe elements are hard-coded to be focusable, but unlike other
focusable elements (like text fields) this is almost always invisible
to the user.  This disables the 'is focusable' check for the special
case of iframes.  Iframes can still be candidates for adjustment for
other reasons (eg. event handlers), as can their contents of course.

BUG=405999

Review URL: https://codereview.chromium.org/495163002

git-svn-id: svn://svn.chromium.org/blink/trunk@180778 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Revert of Directly composited images are images: ASSERT that (patchset #2 of https://codereview.chromium.org/491773002/)

Reason for revert:
Breaking android bots most of the time

Original issue's description:
> Directly composited images are images: ASSERT that
> 
> isDirectlyCompositedImage only applies to images. ASSERT that and
> make callers do all the isImage() testing.
> 
> BUG=405803
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=180721

TBR=vollick@chromium.org,benm@chromium.org,noel@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=405803

Review URL: https://codereview.chromium.org/497143002

git-svn-id: svn://svn.chromium.org/blink/trunk@180779 bbb929c8-8fbe-4397-9dbb-9b2b20218538