RenderObject: don't change GraphicsContext state when not drawing dashed/dotted lines.
RenderObject: don't change GraphicsContext state when not drawing dashed/dotted lines.

Previously, there was asymmetry between changing and restoring state (certain
state would be restored only if thickness was positive, i.e. a line was actually
drawn).

BUG=237311

Review URL: https://chromiumcodereview.appspot.com/14598010

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@149546 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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