Minor build/include fixes for google3 roll.

Change-Id: I2f9ba7f98acdf9441d80d3a1169b36bee44a2e0e
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/108545
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Loko Kung <lokokung@google.com>
Reviewed-by: Austin Eng <enga@chromium.org>

src/dawn/native/stream/Source.h

@@ -17,6 +17,8 @@
 
 #include <cstddef>
 
+#include "dawn/native/Error.h"
+
 namespace dawn::native::stream {
 
 // Interface for a deserialization source.

src/dawn/utils/TestUtils.h

@@ -15,6 +15,8 @@
 #ifndef SRC_DAWN_UTILS_TESTUTILS_H_
 #define SRC_DAWN_UTILS_TESTUTILS_H_
 
+#include <ostream>
+
 #include "dawn/webgpu_cpp.h"
 
 namespace utils {