Add arb_texture_rectangle support properly in GLES3 shaders

src/gpu/gl/GrGLCaps.cpp

Index: src/gpu/gl/GrGLCaps.cpp
diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index c2ace6cd368948d25d60f95b766895dcfd1ce740..d94f4876214f5457bde7547ef1a3d2e314a26b54 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -226,13 +226,19 @@ void GrGLCaps::init(const GrContextOptions& contextOptions,
         }
     }
 
-    if ((kGL_GrGLStandard == standard && version >= GR_GL_VER(3, 1)) ||
-        ctxInfo.hasExtension("GL_ARB_texture_rectangle")) {
-        // We also require textureSize() support for rectangle 2D samplers which was added in GLSL
-        // 1.40.
-        if (ctxInfo.glslGeneration() >= k140_GrGLSLGeneration) {
-            fRectangleTextureSupport = true;
+    if (kGL_GrGLStandard == standard) {
+        if (version >= GR_GL_VER(3, 1) || ctxInfo.hasExtension("GL_ARB_texture_rectangle")) {
+            // We also require textureSize() support for rectangle 2D samplers which was added in
+            // GLSL 1.40.
+            if (ctxInfo.glslGeneration() >= k140_GrGLSLGeneration) {
+                fRectangleTextureSupport = true;
+            }
         }
+    } else {
+        // Command buffer exposes this in GL ES context for Chromium reasons,
+        // but it should not be used. Also, at the time of writing command buffer
+        // lacks TexImage2D support and ANGLE lacks GL ES 3.0 support.
+        fRectangleTextureSupport = ctxInfo.hasExtension("GL_ARB_texture_rectangle");
     }
 
     if (kGL_GrGLStandard == standard) {
@@ -632,6 +638,25 @@ void GrGLCaps::initGLSL(const GrGLContextInfo& ctxInfo) {
             glslCaps->fExternalTextureExtensionString = "GL_OES_EGL_image_external_essl3";
         }
     }
+    if (fRectangleTextureSupport) {
+        if (kGL_GrGLStandard == standard) {
+            // "Conceptually, you can consider the declaration
+            // #extension GL_ARB_texture_rectangle : require, to allow support
+            // for texture rectangles, to be implicitly prepended to every
+            // GLSL shader when ARB_texture_rectangle is advertised."
+            // -->  glslCaps->fRectangleTextureExtensionString == nullptr.
+            glslCaps->fRectangleTextureUseUnifiedTextureFunctionName =
+                    ctxInfo.glslGeneration() >= k130_GrGLSLGeneration;
+        } else {
+            //"All future GLSL extensions should follow the "OpenGL Shading Language
+            // Extension Conventions" however."
+            // We imagine ANGLE implementation allowing ARB_texture_rectangle being
+            // based on an extension text requires the extension string.
+            glslCaps->fRectangleTextureExtensionString = "GL_ARB_texture_rectangle";
+            glslCaps->fRectangleTextureUseUnifiedTextureFunctionName =
+                    ctxInfo.glslGeneration() == k330_GrGLSLGeneration;
+        }
+    }
 
     // The Tegra3 compiler will sometimes never return if we have min(abs(x), 1.0), so we must do
     // the abs first in a separate expression.