Use absl::flat_hash_map instead of std::unordered_map in more places

This patch replaces std::unordered_map with absl::flat_hash_map in
many more places and removes some unused code.

Bug: dawn:1513
Change-Id: I5bcf1f3b099ee19f2b6694946c3b81c8e8877451
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/195634
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>

src/dawn/native/d3d/D3DCompilationRequest.h

diff --git a/src/dawn/native/d3d/D3DCompilationRequest.h b/src/dawn/native/d3d/D3DCompilationRequest.h
index 95c21e6..62dabfd 100644
--- a/src/dawn/native/d3d/D3DCompilationRequest.h
+++ b/src/dawn/native/d3d/D3DCompilationRequest.h
@@ -30,9 +30,7 @@
 
 #include <d3dcompiler.h>
 
-#include <string>
-#include <unordered_map>
-#include <vector>
+#include <string_view>
 
 #include "dawn/native/CacheRequest.h"
 #include "dawn/native/Serializable.h"
@@ -57,8 +55,6 @@
 
 enum class Compiler { FXC, DXC };
 
-using AccessControl = std::unordered_map<tint::BindingPoint, tint::core::Access>;
-
 using InterStageShaderVariablesMask = std::bitset<tint::hlsl::writer::kMaxInterStageLocations>;
 
 #define HLSL_COMPILATION_REQUEST_MEMBERS(X)                                                      \

src/dawn/native/opengl/BindingPoint.h

diff --git a/src/dawn/native/opengl/BindingPoint.h b/src/dawn/native/opengl/BindingPoint.h
index 86bf647..6b4a59e 100644
--- a/src/dawn/native/opengl/BindingPoint.h
+++ b/src/dawn/native/opengl/BindingPoint.h
@@ -28,9 +28,9 @@
 #ifndef SRC_DAWN_NATIVE_OPENGL_BINDPOINT_H_
 #define SRC_DAWN_NATIVE_OPENGL_BINDPOINT_H_
 
-#include <unordered_map>
 #include <utility>
 
+#include "absl/container/flat_hash_map.h"
 #include "src/tint/api/common/binding_point.h"
 
 namespace dawn::native::opengl {
@@ -46,7 +46,7 @@
 /// Records the field and the byte offset of the data to push in the internal uniform buffer.
 using FunctionAndOffset = std::pair<BindPointFunction, uint32_t>;
 /// Maps from binding point to data entry with the information to populate the data.
-using BindingPointToFunctionAndOffset = std::unordered_map<tint::BindingPoint, FunctionAndOffset>;
+using BindingPointToFunctionAndOffset = absl::flat_hash_map<tint::BindingPoint, FunctionAndOffset>;
 
 }  // namespace dawn::native::opengl
 

src/dawn/native/opengl/ShaderModuleGL.cpp

diff --git a/src/dawn/native/opengl/ShaderModuleGL.cpp b/src/dawn/native/opengl/ShaderModuleGL.cpp
index b5dc23a..34d3539 100644
--- a/src/dawn/native/opengl/ShaderModuleGL.cpp
+++ b/src/dawn/native/opengl/ShaderModuleGL.cpp
@@ -28,9 +28,9 @@
 #include "dawn/native/opengl/ShaderModuleGL.h"
 
 #include <sstream>
-#include <unordered_map>
 #include <utility>
 
+#include "absl/container/flat_hash_map.h"
 #include "dawn/native/BindGroupLayoutInternal.h"
 #include "dawn/native/CacheRequest.h"
 #include "dawn/native/Pipeline.h"
@@ -42,7 +42,7 @@
 #include "dawn/platform/DawnPlatform.h"
 #include "dawn/platform/tracing/TraceEvent.h"
 
-#include "tint/tint.h"
+#include "src/tint/api/common/binding_point.h"
 
 namespace dawn::native {
 namespace {
@@ -69,7 +69,7 @@
     DAWN_UNREACHABLE();
 }
 
-using BindingMap = std::unordered_map<tint::BindingPoint, tint::BindingPoint>;
+using BindingMap = absl::flat_hash_map<tint::BindingPoint, tint::BindingPoint>;
 
 opengl::CombinedSampler* AppendCombinedSampler(opengl::CombinedSamplerInfo* info,
                                                tint::BindingPoint texture,