Disable flat interpolation in TextureOp on Qualcomm

Change-Id: I335fa9731cbf449989242f7e81096248abc90e90
Reviewed-on: https://skia-review.googlesource.com/46980
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/vk/GrVkCaps.cpp b/src/gpu/vk/GrVkCaps.cpp
index 6d5b601..945f87f 100644
--- a/src/gpu/vk/GrVkCaps.cpp
+++ b/src/gpu/vk/GrVkCaps.cpp
@@ -234,6 +234,9 @@
     // Vulkan is based off ES 3.0 so the following should all be supported
     shaderCaps->fUsesPrecisionModifiers = true;
     shaderCaps->fFlatInterpolationSupport = true;
+    // Flat interpolation appears to be slow on Qualcomm GPUs. This was tested in GL and is assumed
+    // to be true with Vulkan as well.
+    shaderCaps->fPreferFlatInterpolation = kQualcomm_VkVendor != properties.vendorID;
 
     // GrShaderCaps