Nuke Builders Part 1: remove the testing BufferBuilder.

This requires deleting wire tests for builders that were using it, and
leads to small simplifications in the WireTest harness. Also allows
removing the BuilderBase class from dawn_native.

BUG=dawn:125

Change-Id: I3cbac609207aa652cdc9d37e0b700cce3ac6e093
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/6120
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

src/tests/unittests/wire/WireTest.cpp

@@ -21,7 +21,7 @@
 using namespace testing;
 using namespace dawn_wire;
 
-WireTest::WireTest(bool ignoreSetCallbackCalls) : mIgnoreSetCallbackCalls(ignoreSetCallbackCalls) {
+WireTest::WireTest() {
 }
 
 WireTest::~WireTest() {
@@ -87,8 +87,5 @@ void WireTest::DeleteServer() {
 }
 
 void WireTest::SetupIgnoredCallExpectations() {
-    if (mIgnoreSetCallbackCalls) {
-        EXPECT_CALL(api, OnBuilderSetErrorCallback(_, _, _, _)).Times(AnyNumber());
-    }
     EXPECT_CALL(api, DeviceTick(_)).Times(AnyNumber());
 }