Revert "Revert "Revert "Revert "Revert "Revert "Redefine the meaning of sample counts in GPU backend.""""""

This reverts commit 3a2cc2c2ec124de36d2544b2a523ef1dd317ca32.

Fix code with samplecnt=0 that slipped in between trybots/CQ and landing of previous version

Change-Id: Iab19f2e8d1e9901601c8c76244d7a88c5d707fab
Reviewed-on: https://skia-review.googlesource.com/103181
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/src/gpu/vk/GrVkUtil.cpp b/src/gpu/vk/GrVkUtil.cpp
index cb0046e..12db4c1 100644
--- a/src/gpu/vk/GrVkUtil.cpp
+++ b/src/gpu/vk/GrVkUtil.cpp
@@ -263,8 +263,8 @@
 }
 
 bool GrSampleCountToVkSampleCount(uint32_t samples, VkSampleCountFlagBits* vkSamples) {
+    SkASSERT(samples >= 1);
     switch (samples) {
-        case 0: // fall through
         case 1:
             *vkSamples = VK_SAMPLE_COUNT_1_BIT;
             return true;