tint: Fix utils::Vector<T, 0>::Push segfaulting

Grow multiplies capacity by 2, but for a 0-sized Vector (i.e. no small
array), capacity is 0, so Grow wouldn't grow.

Bug: tint:1613
Change-Id: I6f2954cbfdb0c638e02b2f441e17a016c0198ad7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/98540
Commit-Queue: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/tint/utils/vector.h

@@ -17,6 +17,7 @@
 
 #include <stddef.h>
 #include <stdint.h>
+#include <algorithm>
 #include <array>
 #include <iterator>
 #include <utility>
@@ -461,7 +462,7 @@ class Vector {
     }
 
     /// Expands the capacity of the vector
-    void Grow() { Reserve(impl_.slice.cap * 2); }
+    void Grow() { Reserve(std::max(impl_.slice.cap, static_cast<size_t>(1)) * 2); }
 
     /// Moves 'other' to this vector, if possible, otherwise performs a copy.
     void MoveOrCopy(VectorRef<T>&& other) {

src/tint/utils/vector_test.cc

@@ -151,6 +151,17 @@ TEST(TintVectorTest, InitializerList_NoSmallArray) {
     EXPECT_TRUE(AllExternallyHeld(vec));
 }
 
+TEST(TintVectorTest, Push_NoSmallArray) {
+    Vector<std::string, 0> vec;
+    vec.Push("one");
+    vec.Push("two");
+    EXPECT_EQ(vec.Length(), 2u);
+    EXPECT_EQ(vec.Capacity(), 2u);
+    EXPECT_EQ(vec[0], "one");
+    EXPECT_EQ(vec[1], "two");
+    EXPECT_TRUE(AllExternallyHeld(vec));
+}
+
 TEST(TintVectorTest, InferTN_1CString) {
     auto vec = Vector{"one"};
     static_assert(std::is_same_v<decltype(vec)::value_type, const char*>);