Revert of Refactor drawContext/RenderTarget creation

src/effects/SkAlphaThresholdFilter.cpp

Index: src/effects/SkAlphaThresholdFilter.cpp
diff --git a/src/effects/SkAlphaThresholdFilter.cpp b/src/effects/SkAlphaThresholdFilter.cpp
index cec45ba9114243cb9ba768ee9b7585226e216604..bfbcfd21f8b959e8acfeeab9fc0c0e41a032457c 100644
--- a/src/effects/SkAlphaThresholdFilter.cpp
+++ b/src/effects/SkAlphaThresholdFilter.cpp
@@ -95,16 +95,24 @@
 sk_sp<GrTexture> SkAlphaThresholdFilterImpl::createMaskTexture(GrContext* context,
                                                                const SkMatrix& inMatrix,
                                                                const SkIRect& bounds) const {
-    GrPixelConfig config;
+    GrSurfaceDesc maskDesc;
     if (context->caps()->isConfigRenderable(kAlpha_8_GrPixelConfig, false)) {
-        config = kAlpha_8_GrPixelConfig;
+        maskDesc.fConfig = kAlpha_8_GrPixelConfig;
     } else {
-        config = kRGBA_8888_GrPixelConfig;
-    }
-
-    sk_sp<GrDrawContext> drawContext(context->newDrawContext(GrContext::kLoose_BackingFit,
-                                                             bounds.width(), bounds.height(),
-                                                             config));
+        maskDesc.fConfig = kRGBA_8888_GrPixelConfig;
+    }
+    maskDesc.fFlags = kRenderTarget_GrSurfaceFlag;
+    // Add one pixel of border to ensure that clamp mode will be all zeros
+    // the outside.
+    maskDesc.fWidth = bounds.width();
+    maskDesc.fHeight = bounds.height();
+    sk_sp<GrTexture> maskTexture(context->textureProvider()->createApproxTexture(maskDesc));
+    if (!maskTexture) {
+        return nullptr;
+    }
+
+    sk_sp<GrDrawContext> drawContext(
+                                context->drawContext(sk_ref_sp(maskTexture->asRenderTarget())));
     if (!drawContext) {
         return nullptr;
     }
@@ -121,7 +129,7 @@
         iter.next();
     }
 
-    return drawContext->asTexture();
+    return maskTexture;
 }
 #endif