Use noperspective interpolation for 2D draws

Adds a mechanism to notify GrGLSLVaryingHandler that a shader will not
emit geometry in perspective. This gives it a chance to use the
noperspective keyword if it is supported.

Updates the existing processors to notify the varying handler when
there is no perspective.

Begins using the noperspective keyword in GrGLGpu internal shaders.

Web scenes with observable benefit (Pixel C, gpu config):

  tabl_nofolo.skp        4.62 -> 3.33 ms   28%
  desk_tigersvg.skp      26.5 -> 24 ms      9%
  desk_pokemonwiki.skp   16.1 -> 14.9 ms    7%
  tabl_deviantart.skp    3.97 -> 3.7 ms     7%
  desk_gws.skp           3.85 -> 3.65 ms    5%

Also adds new methods for creating varyings with flat interpolation.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1673093002

Review URL: https://codereview.chromium.org/1673093002

1 files changed, 6 insertions, 1 deletions

diff --git a/src/gpu/GrPathProcessor.cpp b/src/gpu/GrPathProcessor.cpp
index cb33010f7e..1d70dea289 100644
--- a/src/gpu/GrPathProcessor.cpp
+++ b/src/gpu/GrPathProcessor.cpp
@@ -22,13 +22,18 @@ public:
                        const GrGLSLCaps&,
                        GrProcessorKeyBuilder* b) {
         b->add32(SkToInt(pathProc.overrides().readsColor()) |
-                 SkToInt(pathProc.overrides().readsCoverage()) << 16);
+                 (SkToInt(pathProc.overrides().readsCoverage()) << 1) |
+                 (SkToInt(pathProc.viewMatrix().hasPerspective()) << 2));
     }
 
     void emitCode(EmitArgs& args) override {
         GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
         const GrPathProcessor& pathProc = args.fGP.cast<GrPathProcessor>();
 
+        if (!pathProc.viewMatrix().hasPerspective()) {
+            args.fVaryingHandler->setNoPerspective();
+        }
+
         // emit transforms
         this->emitTransforms(args.fVaryingHandler, args.fTransformsIn, args.fTransformsOut);