fix unsigned/signed warning on linux for GrVkDescriptorPool::numPoolSizes()

src/gpu/vk/GrVkDescriptorPool.cpp

Index: src/gpu/vk/GrVkDescriptorPool.cpp
diff --git a/src/gpu/vk/GrVkDescriptorPool.cpp b/src/gpu/vk/GrVkDescriptorPool.cpp
index d4dced6c32c35c7f6a1130cc16ece19bd9adcfce..48880b64db2c32c9951113eda11baa1746055c11 100644
--- a/src/gpu/vk/GrVkDescriptorPool.cpp
+++ b/src/gpu/vk/GrVkDescriptorPool.cpp
@@ -14,7 +14,7 @@
 GrVkDescriptorPool::GrVkDescriptorPool(const GrVkGpu* gpu, const DescriptorTypeCounts& typeCounts)
     : INHERITED()
     , fTypeCounts(typeCounts) {
-    uint32_t numPools = fTypeCounts.numPoolSizes();
+    int numPools = fTypeCounts.numPoolSizes();
     SkAutoTDeleteArray<VkDescriptorPoolSize> poolSizes(new VkDescriptorPoolSize[numPools]);
     int currentPool = 0;
     for (int i = VK_DESCRIPTOR_TYPE_BEGIN_RANGE; i < VK_DESCRIPTOR_TYPE_END_RANGE; ++i) {
@@ -57,8 +57,8 @@ void GrVkDescriptorPool::freeGPUData(const GrVkGpu* gpu) const {
 
 ///////////////////////////////////////////////////////////////////////////////
 
-uint32_t GrVkDescriptorPool::DescriptorTypeCounts::numPoolSizes() const {
-    uint32_t count = 0;
+int GrVkDescriptorPool::DescriptorTypeCounts::numPoolSizes() const {
+    int count = 0;
     for (int i = VK_DESCRIPTOR_TYPE_BEGIN_RANGE; i < VK_DESCRIPTOR_TYPE_END_RANGE; ++i) {
         count += fDescriptorTypeCount[i] ? 1 : 0;
     }