Merge 145727 - Fix fade-truncation of LTR tab titles under RTL UI.

Merge 145727 - Fix fade-truncation of LTR tab titles under RTL UI.

This was regressed by http://crrev.com/145435, which
made UpdateRenderText() get a default alignment based
on the UI directionality in the case where |flags|
didn't specify one.

This caused an issue for DrawFadeTruncatingString(),
which assumed that the default alignment would LTR
unless specified otherwise.

This CL fixes the issue by having DrawFadeTruncatingString()
specify LTR alignment whenever it doesn't explicitly set
it to RTL, which matches its behavior before r145435.

BUG=135639
TEST=Open chrome.exe --lang=he and go to amazon.com. The
tab title, which should be in English, should be fade
truncated on the right end. Go to http://www.haaretz.co.il
and text should be fade truncated on the left end. When
launched in LTR mode (chrome.exe --lang=en), both of those
tab titles should be fade-truncated on right, per the M19
behavior.

Review URL: https://chromiumcodereview.appspot.com/10743002

TBR=asvitkine@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=145918