Revert of Patch to remove constant attributes (patchset #6 id:100001 of https://codereview.chromium.org/678073005/)

Reason for revert:
Breaks the K1

Original issue's description:
> Working patch to remove constant attributes.  This may cause some gm mismatches, I will rebaseline tonight.
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/84c94c0dfd1e12e97d8a835882dda575f36e41d2

TBR=bsalomon@google.com,egdaniel@google.com,joshualitt@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/679363002
diff --git a/src/gpu/gl/GrGLProgramDesc.cpp b/src/gpu/gl/GrGLProgramDesc.cpp
index 733de13..7908813 100644
--- a/src/gpu/gl/GrGLProgramDesc.cpp
+++ b/src/gpu/gl/GrGLProgramDesc.cpp
@@ -257,8 +257,8 @@
 
     header->fEmitsPointSize = GrGpu::kDrawPoints_DrawType == drawType;
 
-    bool isPathRendering = GrGpu::IsPathRenderingDrawType(drawType);
-    if (gpu->caps()->pathRenderingSupport() && isPathRendering &&
+    if (gpu->caps()->pathRenderingSupport() &&
+        GrGpu::IsPathRenderingDrawType(drawType) &&
         gpu->glPathRendering()->texturingMode() == GrGLPathRendering::FixedFunction_TexturingMode) {
         header->fUseFragShaderOnly = true;
         SkASSERT(!optState.hasGeometryProcessor());
@@ -266,15 +266,12 @@
         header->fUseFragShaderOnly = false;
     }
 
-    bool hasUniformColor = inputColorIsUsed &&
-                           (isPathRendering || !optState.hasColorVertexAttribute());
-
-    bool hasUniformCoverage = inputCoverageIsUsed &&
-                              (isPathRendering || !optState.hasCoverageVertexAttribute());
+    bool defaultToUniformInputs = GrGpu::IsPathRenderingDrawType(drawType) ||
+                                  GR_GL_NO_CONSTANT_ATTRIBUTES;
 
     if (!inputColorIsUsed) {
         header->fColorInput = kAllOnes_ColorInput;
-    } else if (hasUniformColor) {
+    } else if (defaultToUniformInputs && !optState.hasColorVertexAttribute()) {
         header->fColorInput = kUniform_ColorInput;
     } else {
         header->fColorInput = kAttribute_ColorInput;
@@ -286,7 +283,7 @@
 
     if (covIsSolidWhite || !inputCoverageIsUsed) {
         header->fCoverageInput = kAllOnes_ColorInput;
-    } else if (hasUniformCoverage) {
+    } else if (defaultToUniformInputs && !optState.hasCoverageVertexAttribute()) {
         header->fCoverageInput = kUniform_ColorInput;
     } else {
         header->fCoverageInput = kAttribute_ColorInput;