Do div-by-zero check for all gpus in ellipse/rr effects.

src/gpu/effects/GrRRectEffect.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrRRectEffect.h"
 
 #include "gl/GrGLEffect.h"
@@ skipping 554 matching lines @@
                                    invRadiiLTRBSqdName, invRadiiLTRBSqdName);
             break;
         }
         default:
             GrCrash("RRect should always be simple or nine-patch.");
     }
     // implicit is the evaluation of (x/a)^2 + (y/b)^2 - 1.
     builder->fsCodeAppend("\t\tfloat implicit = dot(Z, dxy) - 1.0;\n");
     // grad_dot is the squared length of the gradient of the implicit.
     builder->fsCodeAppendf("\t\tfloat grad_dot = 4.0 * dot(Z, Z);\n");
-    if (builder->ctxInfo().caps()->dropsTileOnZeroDivide()) {
-        builder->fsCodeAppend("\t\tgrad_dot = max(grad_dot, 1.0e-4);\n");
-    }
+    // avoid calling inversesqrt on zero.
+    builder->fsCodeAppend("\t\tgrad_dot = max(grad_dot, 1.0e-4);\n");
     builder->fsCodeAppendf("\t\tfloat approx_dist = implicit * inversesqrt(grad_dot);\n");
 
     if (kFillAA_GrEffectEdgeType == erre.getEdgeType()) {
         builder->fsCodeAppend("\t\tfloat alpha = clamp(0.5 - approx_dist, 0.0, 1.0);\n");
     } else {
         builder->fsCodeAppend("\t\tfloat alpha = clamp(0.5 + approx_dist, 0.0, 1.0);\n");
     }
 
     builder->fsCodeAppendf("\t\t%s = %s;\n", outputColor,
                            (GrGLSLExpr4(inputColor) * GrGLSLExpr1("alpha")).c_str());
@@ skipping 134 matching lines @@
                 if (rrect.isNinePatch()) {
                     return EllipticalRRectEffect::Create(edgeType, rrect);
                 }
                 return NULL;
             }
         }
     }
 
     return NULL;
 }