Add fine-grained speed profiling inside MarkupParser

BUG=435264
R=nyquist@chromium.org

Review URL: https://codereview.chromium.org/723373003
Optimize OpenGraphProtocolParser.parseMetaTags for speed

Time spent on parseMetaTags decreased from 8.7+-0.5 to 6.1+-0.3(ms) for:
http://www.cnn.com/2014/11/06/world/syria-strike/index.html

BUG=None
R=cjhopman@chromium.org

Review URL: https://codereview.chromium.org/725573006
Optimize SchemaOrgParser.parse for speed

Time spent on SchemaOrgParser.parse decreased from 43+-2 to 5.0+-0.2(ms) for:
http://www.nydailynews.com/entertainment/gossip/1.2007257

BUG=None
R=cjhopman@chromium.org

Review URL: https://codereview.chromium.org/724303002
Remove gwt-2.5.1 and gwt_exporter

These are no longer used.
Fix TextDocumentConstruction expectations

In the new gwt's test environment, <em> has inline style (instead of
block). This affects the tag levels of the constructed text blocks.

R=nyquist@chromium.org

Review URL: https://codereview.chromium.org/773843003
Make image source absolute.

This change is to fix a bug where image URLs are collected before
the distiller makes them absolute. The code is essentially the same
as before but has been moved to a new position. An additional small
test has been added to check this.

BUG=435371
R=nyquist@chromium.org

Review URL: https://codereview.chromium.org/739393006
Add .clang-format file to enable git cl format

R=wychen@chromium.org

Review URL: https://codereview.chromium.org/789653003