OpenGL: delete shaders and pipelines when they are not used any longer

Previously on OpenGL backend the GL pipelines and shaders are never
deleted. With this patch the GL pipelines and shaders will be able to
be destroyed correctly after they are not needed any longer.

BUG=dawn:529

Change-Id: I4f7f22c7b536825363fe1ecc0f5ffd1bb86fd774
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/65140
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Stephen White <senorblanco@chromium.org>
Commit-Queue: Jiawei Shao <jiawei.shao@intel.com>

src/dawn_native/opengl/ComputePipelineGL.cpp

@@ -27,6 +27,10 @@ namespace dawn_native { namespace opengl {
         return pipeline;
     }
 
+    ComputePipeline::~ComputePipeline() {
+        DeleteProgram(ToBackend(GetDevice())->gl);
+    }
+
     MaybeError ComputePipeline::Initialize() {
         DAWN_TRY(
             InitializeBase(ToBackend(GetDevice())->gl, ToBackend(GetLayout()), GetAllStages()));

src/dawn_native/opengl/ComputePipelineGL.h

@@ -35,7 +35,7 @@ namespace dawn_native { namespace opengl {
 
       private:
         using ComputePipelineBase::ComputePipelineBase;
-        ~ComputePipeline() override = default;
+        ~ComputePipeline() override;
         MaybeError Initialize() override;
     };
 

src/dawn_native/opengl/PipelineGL.cpp

@@ -87,6 +87,7 @@ namespace dawn_native { namespace opengl {
         // Create an OpenGL shader for each stage and gather the list of combined samplers.
         PerStage<CombinedSamplerInfo> combinedSamplers;
         bool needsDummySampler = false;
+        std::vector<GLuint> glShaders;
         for (SingleShaderStage stage : IterateStages(activeStages)) {
             const ShaderModule* module = ToBackend(stages[stage].module.Get());
             std::string glsl;
@@ -96,6 +97,7 @@ namespace dawn_native { namespace opengl {
             GLuint shader;
             DAWN_TRY_ASSIGN(shader, CreateShader(gl, GLShaderType(stage), glsl.c_str()));
             gl.AttachShader(mProgram, shader);
+            glShaders.push_back(shader);
         }
 
         if (needsDummySampler) {
@@ -178,9 +180,19 @@ namespace dawn_native { namespace opengl {
 
             textureUnit++;
         }
+
+        for (GLuint glShader : glShaders) {
+            gl.DetachShader(mProgram, glShader);
+            gl.DeleteShader(glShader);
+        }
+
         return {};
     }
 
+    void PipelineGL::DeleteProgram(const OpenGLFunctions& gl) {
+        gl.DeleteProgram(mProgram);
+    }
+
     const std::vector<PipelineGL::SamplerUnit>& PipelineGL::GetTextureUnitsForSampler(
         GLuint index) const {
         ASSERT(index < mUnitsForSamplers.size());

src/dawn_native/opengl/PipelineGL.h

@@ -47,12 +47,12 @@ namespace dawn_native { namespace opengl {
         const std::vector<GLuint>& GetTextureUnitsForTextureView(GLuint index) const;
         GLuint GetProgramHandle() const;
 
-        void ApplyNow(const OpenGLFunctions& gl);
-
       protected:
+        void ApplyNow(const OpenGLFunctions& gl);
         MaybeError InitializeBase(const OpenGLFunctions& gl,
                                   const PipelineLayout* layout,
                                   const PerStage<ProgrammableStage>& stages);
+        void DeleteProgram(const OpenGLFunctions& gl);
 
       private:
         GLuint mProgram;

src/dawn_native/opengl/RenderPipelineGL.cpp

@@ -240,6 +240,7 @@ namespace dawn_native { namespace opengl {
         const OpenGLFunctions& gl = ToBackend(GetDevice())->gl;
         gl.DeleteVertexArrays(1, &mVertexArrayObject);
         gl.BindVertexArray(0);
+        DeleteProgram(gl);
     }
 
     GLenum RenderPipeline::GetGLPrimitiveTopology() const {