Runtime Effects: Support 'uniform shader' (vs. 'in shader')

The previous behavior leaked Skia-internal concepts into public SkSL.
Users coming from GLSL will expect that bindable/sampleable objects are
uniform (just like texture2D). This keeps the old support around (and
tested), but updates all of our examples to use 'uniform'.

Bug: skia:10679
Change-Id: I0c98162f5e21dad7014d9778ceb26143d2f6030e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/332376
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
diff --git a/gm/runtimeshader.cpp b/gm/runtimeshader.cpp
index 9200238..b7ca692 100644
--- a/gm/runtimeshader.cpp
+++ b/gm/runtimeshader.cpp
@@ -120,9 +120,9 @@
 class ThresholdRT : public RuntimeShaderGM {
 public:
     ThresholdRT() : RuntimeShaderGM("threshold_rt", {256, 256}, R"(
-        in shader before_map;
-        in shader after_map;
-        in shader threshold_map;
+        uniform shader before_map;
+        uniform shader after_map;
+        uniform shader threshold_map;
 
         uniform float cutoff;
         uniform float slope;
@@ -218,8 +218,8 @@
 class ColorCubeRT : public RuntimeShaderGM {
 public:
     ColorCubeRT() : RuntimeShaderGM("color_cube_rt", {512, 512}, R"(
-        in shader input;
-        in shader color_cube;
+        uniform shader input;
+        uniform shader color_cube;
 
         uniform float rg_scale;
         uniform float rg_bias;
@@ -303,7 +303,7 @@
     // This test also *explicitly* doesn't include coords in main's parameter list, to test that
     // runtime shaders work without them being declared (when they're not used).
     DefaultColorRT() : RuntimeShaderGM("default_color_rt", {512, 256}, R"(
-        in shader input;
+        uniform shader input;
         half4 main() {
             return sample(input);
         }