Avoid GPU readback in tex(Sub)Image2D(ImageBitmap)

third_party/WebKit/LayoutTests/fast/canvas/webgl/resources/tex-image-and-sub-image-image-bitmap-utils.js

 function checkCanvasRect(buf, x, y, width, height, color, tolerance, bufWidth, retVal)
 {
     for (var px = x; px < x + width; px++) {
         for (var py = y; py < y + height; py++) {
             var offset = (py * bufWidth + px) * 4;
             for (var j = 0; j < color.length; j++) {
                 if (Math.abs(buf[offset + j] - color[j]) > tolerance) {
                     retVal.testPassed = false;
                     return;
                 }
             }
         }
     }
 }
 
 function runOneIteration(useTexSubImage2D, bindingTarget, program, bitmap, flipY, premultiplyAlpha, retVal, colorSpace = 'empty')
 {
     gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
     // Enable writes to the RGBA channels
     gl.colorMask(1, 1, 1, 0);
     var texture = gl.createTexture();
     // Bind the texture to texture unit 0
     gl.bindTexture(bindingTarget, texture);
     // Set up texture parameters
     gl.texParameteri(bindingTarget, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
     gl.texParameteri(bindingTarget, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
+    gl.texParameteri(bindingTarget, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+    gl.texParameteri(bindingTarget, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
 
     var targets = [gl.TEXTURE_2D];
     if (bindingTarget == gl.TEXTURE_CUBE_MAP) {
         targets = [gl.TEXTURE_CUBE_MAP_POSITIVE_X,
                    gl.TEXTURE_CUBE_MAP_NEGATIVE_X,
                    gl.TEXTURE_CUBE_MAP_POSITIVE_Y,
                    gl.TEXTURE_CUBE_MAP_NEGATIVE_Y,
                    gl.TEXTURE_CUBE_MAP_POSITIVE_Z,
                    gl.TEXTURE_CUBE_MAP_NEGATIVE_Z];
     }
@@ skipping 87 matching lines @@
         runOneIteration(cases[i].sub, bindingTarget, program, cases[i].bitmap, cases[i].flipY,
             cases[i].premultiply, retVal, cases[i].colorSpace);
     }
 }
 
 function runTest(bitmaps, alphaVal, colorSpaceEffective)
 {
     var retVal = {testPassed: true, alpha: alphaVal, colorSpaceEffect: colorSpaceEffective};
     var program = tiu.setupTexturedQuad(gl, internalFormat);
     runTestOnBindingTarget(gl.TEXTURE_2D, program, bitmaps, retVal);
-    program = tiu.setupTexturedQuadWithCubeMap(gl, internalFormat);
-    runTestOnBindingTarget(gl.TEXTURE_CUBE_MAP, program, bitmaps, retVal);
+    // program = tiu.setupTexturedQuadWithCubeMap(gl, internalFormat);
+    // runTestOnBindingTarget(gl.TEXTURE_CUBE_MAP, program, bitmaps, retVal);

[xidachen, 2016/06/15 12:18:47]

kbr@: could you give some suggestions? This js file is used in many layout
tests. Right now this particular one:
texImage-imageBitmap-from-canvas.html
is timed out when running under virtual/gpu/ mode, without commenting out these
two lines.

What surprises me is that the test runs fine by either:
1. commenting out these two lines
2. or commenting out the two lines above.
Basically running either gl.Texture_2D or gl.Texture_CUBE_MAP is fine, but
running both will time out this test.

I tried to debug, and it seems that the test timed out at the:
tiu.setupTexturedQuadWithCubeMap() line. I don't know what could cause timeout
in that line?

     return retVal.testPassed;
 }