Enable Skia readback on Linux

Bug: 1033001
Change-Id: Iafecf2e001c7c6535db1444c18bb4190bc8e5014
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2039592Reviewed-by: kylechar <kylechar@chromium.org>
Commit-Queue: Jonathan Backer <backer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#739055}

cc/trees/layer_tree_host_pixeltest_readback.cc

@@ -421,7 +421,7 @@ ReadbackTestConfig const kTestConfigs[] = {
     ReadbackTestConfig{LayerTreeTest::RENDERER_GL, READBACK_TEXTURE},
     ReadbackTestConfig{LayerTreeTest::RENDERER_GL, READBACK_BITMAP},
 #if defined(GL_ON_PLATFORM)
-#if !defined(OS_WIN)
+#if !defined(OS_WIN) && !defined(OS_LINUX)
     // TODO(crbug.com/1046788): The skia readback path doesn't support
     // RGBA_TEXTURE readback requests yet. Don't run these tests on platforms
     // that have UseSkiaForGLReadback enabled by default.
@@ -445,7 +445,7 @@ ReadbackTestConfig const kMaybeVulkanTestConfigs[] = {
     ReadbackTestConfig{LayerTreeTest::RENDERER_GL, READBACK_TEXTURE},
     ReadbackTestConfig{LayerTreeTest::RENDERER_GL, READBACK_BITMAP},
 #if defined(GL_ON_PLATFORM)
-#if !defined(OS_WIN)
+#if !defined(OS_WIN) && !defined(OS_LINUX)
     // TODO(crbug.com/1046788): The skia readback path doesn't support
     // RGBA_TEXTURE readback requests yet. Don't run these tests on platforms
     // that have UseSkiaForGLReadback enabled by default.

components/viz/common/features.cc

@@ -22,7 +22,7 @@ const base::Feature kDynamicColorGamut{"DynamicColorGamut",
                                        base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Use Skia's readback API instead of GLRendererCopier.
-#if defined(OS_WIN)
+#if defined(OS_WIN) || defined(OS_LINUX)
 const base::Feature kUseSkiaForGLReadback{"UseSkiaForGLReadback",
                                           base::FEATURE_ENABLED_BY_DEFAULT};
 #else