Texture: Add helper to query desc from index.

src/libANGLE/Texture.cpp

@@ -455,6 +455,11 @@ void TextureState::setImageDesc(GLenum target, size_t level, const ImageDesc &de
     invalidateCompletenessCache();
 }
 
+const ImageDesc &TextureState::getImageDesc(const ImageIndex &imageIndex) const
+{
+    return getImageDesc(imageIndex.type, imageIndex.mipIndex);
+}
+
 void TextureState::setImageDescChain(GLuint baseLevel,
                                      GLuint maxLevel,
                                      Extents baseSize,
@@ -1235,12 +1240,12 @@ Error Texture::setEGLImageTarget(GLenum target, egl::Image *imageTarget)
 
 Extents Texture::getAttachmentSize(const FramebufferAttachment::Target &target) const
 {
-    return mState.getImageDesc(target.textureIndex().type, target.textureIndex().mipIndex).size;
+    return mState.getImageDesc(target.textureIndex()).size;
 }
 
 const Format &Texture::getAttachmentFormat(const FramebufferAttachment::Target &target) const
 {
-    return getFormat(target.textureIndex().type, target.textureIndex().mipIndex);
+    return mState.getImageDesc(target.textureIndex()).format;
 }
 
 GLsizei Texture::getAttachmentSamples(const FramebufferAttachment::Target &target) const

src/libANGLE/Texture.h

@@ -103,6 +103,7 @@ struct TextureState final : public angle::NonCopyable
     void invalidateCompletenessCache();
 
     const ImageDesc &getImageDesc(GLenum target, size_t level) const;
+    const ImageDesc &getImageDesc(const ImageIndex &imageIndex) const;
 
     GLenum getTarget() const { return mTarget; }
     const SwizzleState &getSwizzleState() const { return mSwizzleState; }