Move the ast node ownership from Context to Module

Fixes: tint:335
Change-Id: I128e229daa56d43e7227ecab72269be33b3ee012
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/33240
Commit-Queue: Ben Clayton <bclayton@google.com>
Auto-Submit: Ben Clayton <bclayton@google.com>
Reviewed-by: dan sinclair <dsinclair@chromium.org>
diff --git a/src/writer/spirv/builder_function_decoration_test.cc b/src/writer/spirv/builder_function_decoration_test.cc
index 8b59b2e..161966c 100644
--- a/src/writer/spirv/builder_function_decoration_test.cc
+++ b/src/writer/spirv/builder_function_decoration_test.cc
@@ -105,9 +105,9 @@
   EXPECT_TRUE(b.GenerateGlobalVariable(v_out)) << b.error();
   EXPECT_TRUE(b.GenerateGlobalVariable(v_wg)) << b.error();
 
-  mod.AddGlobalVariable(v_in);
-  mod.AddGlobalVariable(v_out);
-  mod.AddGlobalVariable(v_wg);
+  mod->AddGlobalVariable(v_in);
+  mod->AddGlobalVariable(v_out);
+  mod->AddGlobalVariable(v_wg);
 
   ASSERT_TRUE(b.GenerateFunction(&func)) << b.error();
   EXPECT_EQ(DumpInstructions(b.debug()), R"(OpName %1 "tint_6d795f696e"
@@ -168,9 +168,9 @@
   EXPECT_TRUE(b.GenerateGlobalVariable(v_out)) << b.error();
   EXPECT_TRUE(b.GenerateGlobalVariable(v_wg)) << b.error();
 
-  mod.AddGlobalVariable(v_in);
-  mod.AddGlobalVariable(v_out);
-  mod.AddGlobalVariable(v_wg);
+  mod->AddGlobalVariable(v_in);
+  mod->AddGlobalVariable(v_out);
+  mod->AddGlobalVariable(v_wg);
 
   ASSERT_TRUE(b.GenerateFunction(&func)) << b.error();
   EXPECT_EQ(DumpInstructions(b.debug()), R"(OpName %1 "tint_6d795f696e"