Update old tools to allow MultiPictureDraw rendering

I'll post a separate patch for nanobench and dm

Review URL: https://codereview.chromium.org/639013003
Make the Sk GL context class an abstract base class

Make the Sk GL context class, SkGLNativeContext, an abstract base class. Before,
it depended on ifdefs to implement the platform dependent polymorphism.  Move
the logic to subclasses of the various platform implementations.

This a step to enable Skia embedders to compile dm and bench_pictures. The
concrete goal is to support running these test apps with Chromium command buffer.

With this change, Chromium can implement its own version of SkGLNativeContext
that uses command buffer, and host the implementation in its own repository.

Implements the above by renaming the SkGLContextHelper to SkGLContext and
removing the unneeded SkGLNativeContext. Also removes
SkGLNativeContext::AutoRestoreContext functionality, it appeared to be unused:
no use in Skia code, and no tests.

BUG=skia:2992

Committed: https://skia.googlesource.com/skia/+/a90ed4e83897b45d6331ee4c54e1edd4054de9a8

Review URL: https://codereview.chromium.org/630843002
Adding 3D lut color filter

Included in this cl is support for 3D textures.

BUG=skia:

Review URL: https://codereview.chromium.org/580863004
use real pdfdevice behind SkDocument

BUG=skia:
TBR=bungeman@google.com

Review URL: https://codereview.chromium.org/645563002
Draw more accurate thick-stroked Beziers (disabled)

Draw thick-stroked Beziers by computing the outset quadratic, measuring the error, and subdividing until the error is within a predetermined limit.

To try this CL out, change src/core/SkStroke.h:18 to

  #define QUAD_STROKE_APPROXIMATION 1

or from the command line: CPPFLAGS="-D QUAD_STROKE_APPROXIMATION=1" ./gyp_skia

Here's what's in this CL:

bench/BezierBench.cpp : a microbench for examining where the time is going
gm/beziers.cpp        : random Beziers with various thicknesses
gm/smallarc.cpp       : a distillation of bug skia:2769
samplecode/SampleRotateCircles.cpp : controls added for error, limit, width
src/core/SkStroke.cpp : the new stroke implementation (disabled)
tests/StrokerTest.cpp : a stroke torture test that checks normal and extreme values

The new stroke algorithm has a tweakable parameter:

  stroker.setError(1);  (SkStrokeRec.cpp:112)

The stroke error is the allowable gap between the midpoint of the stroke quadratic and the center Bezier. As the projection from the quadratic approaches the endpoints, the error is decreased proportionally so that it is always inside the quadratic curve.

An overview of how this works:
- For a given T range of a Bezier, compute the perpendiculars and find the points outset and inset for some radius.
- Construct tangents for the quadratic stroke.
- If the tangent don't intersect between them (may happen with cubics), subdivide.
- If the quadratic stroke end points are close (again, may happen with cubics), draw a line between them.
- Compute the quadratic formed by the intersecting tangents.
- If the midpoint of the quadratic is close to the midpoint of the Bezier perpendicular, return the quadratic.
- If the end of the stroke at the Bezier midpoint doesn't intersect the quad's bounds, subdivide.
- Find where the Bezier midpoint ray intersects the quadratic.
- If the intersection is too close to the quad's endpoints, subdivide.
- If the error is large proportional to the intersection's distance to the quad's endpoints, subdivide.

BUG=skia:723,skia:2769

Review URL: https://codereview.chromium.org/558163005