Add helper to create random AsFPArgs for Ganesh unit tests

Reduces copy-paste and eases maintenance. I'll be adding another field to
AsFPArgs soon, and this is going to streamline that change.

BUG=skia:

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=3639

Change-Id: I6372ed5dce50a5ba9d73039bd4714e34502a1f75
Reviewed-on: https://skia-review.googlesource.com/3639
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
diff --git a/src/effects/gradients/SkTwoPointConicalGradient_gpu.cpp b/src/effects/gradients/SkTwoPointConicalGradient_gpu.cpp
index 8eb8b63..1275be7 100644
--- a/src/effects/gradients/SkTwoPointConicalGradient_gpu.cpp
+++ b/src/effects/gradients/SkTwoPointConicalGradient_gpu.cpp
@@ -207,11 +207,8 @@
         SkGradientShader::MakeTwoPointConical(center1, radius1, center2, radius2,
                                               params.fColors, params.fStops,
                                               params.fColorCount, params.fTileMode);
-    SkMatrix viewMatrix = GrTest::TestMatrix(d->fRandom);
-    auto dstColorSpace = GrTest::TestColorSpace(d->fRandom);
-    sk_sp<GrFragmentProcessor> fp = shader->asFragmentProcessor(SkShader::AsFPArgs(
-        d->fContext, &viewMatrix, NULL, kNone_SkFilterQuality, dstColorSpace.get(),
-        SkSourceGammaTreatment::kRespect));
+    GrTest::TestAsFPArgs asFPArgs(d);
+    sk_sp<GrFragmentProcessor> fp = shader->asFragmentProcessor(asFPArgs.args());
     GrAlwaysAssert(fp);
     return fp;
 }
@@ -485,11 +482,8 @@
         SkGradientShader::MakeTwoPointConical(center1, radius1, center2, radius2,
                                               params.fColors, params.fStops,
                                               params.fColorCount, params.fTileMode);
-    SkMatrix viewMatrix = GrTest::TestMatrix(d->fRandom);
-    auto dstColorSpace = GrTest::TestColorSpace(d->fRandom);
-    sk_sp<GrFragmentProcessor> fp = shader->asFragmentProcessor(SkShader::AsFPArgs(
-        d->fContext, &viewMatrix, NULL, kNone_SkFilterQuality, dstColorSpace.get(),
-        SkSourceGammaTreatment::kRespect));
+    GrTest::TestAsFPArgs asFPArgs(d);
+    sk_sp<GrFragmentProcessor> fp = shader->asFragmentProcessor(asFPArgs.args());
     GrAlwaysAssert(fp);
     return fp;
 }
@@ -691,11 +685,8 @@
         SkGradientShader::MakeTwoPointConical(center1, radius1, center2, radius2,
                                               params.fColors, params.fStops,
                                               params.fColorCount, params.fTileMode);
-    SkMatrix viewMatrix = GrTest::TestMatrix(d->fRandom);
-    auto dstColorSpace = GrTest::TestColorSpace(d->fRandom);
-    sk_sp<GrFragmentProcessor> fp = shader->asFragmentProcessor(SkShader::AsFPArgs(
-        d->fContext, &viewMatrix, NULL, kNone_SkFilterQuality, dstColorSpace.get(),
-        SkSourceGammaTreatment::kRespect));
+    GrTest::TestAsFPArgs asFPArgs(d);
+    sk_sp<GrFragmentProcessor> fp = shader->asFragmentProcessor(asFPArgs.args());
     GrAlwaysAssert(fp);
     return fp;
 }
@@ -939,11 +930,8 @@
         SkGradientShader::MakeTwoPointConical(center1, radius1, center2, radius2,
                                               params.fColors, params.fStops,
                                               params.fColorCount, params.fTileMode);
-    SkMatrix viewMatrix = GrTest::TestMatrix(d->fRandom);
-    auto dstColorSpace = GrTest::TestColorSpace(d->fRandom);
-    sk_sp<GrFragmentProcessor> fp = shader->asFragmentProcessor(SkShader::AsFPArgs(
-        d->fContext, &viewMatrix, NULL, kNone_SkFilterQuality, dstColorSpace.get(),
-        SkSourceGammaTreatment::kRespect));
+    GrTest::TestAsFPArgs asFPArgs(d);
+    sk_sp<GrFragmentProcessor> fp = shader->asFragmentProcessor(asFPArgs.args());
     GrAlwaysAssert(fp);
     return fp;
 }
@@ -1174,11 +1162,8 @@
         SkGradientShader::MakeTwoPointConical(center1, radius1, center2, radius2,
                                               params.fColors, params.fStops,
                                               params.fColorCount, params.fTileMode);
-    SkMatrix viewMatrix = GrTest::TestMatrix(d->fRandom);
-    auto dstColorSpace = GrTest::TestColorSpace(d->fRandom);
-    sk_sp<GrFragmentProcessor> fp = shader->asFragmentProcessor(SkShader::AsFPArgs(
-        d->fContext, &viewMatrix, NULL, kNone_SkFilterQuality, dstColorSpace.get(),
-        SkSourceGammaTreatment::kRespect));
+    GrTest::TestAsFPArgs asFPArgs(d);
+    sk_sp<GrFragmentProcessor> fp = shader->asFragmentProcessor(asFPArgs.args());
     GrAlwaysAssert(fp);
     return fp;
 }