Remove canvas_sub_rectangle failure suppressions on Linux.

After more testing on top-of-tree, it seems that the fix for Issue
713127 should have addressed all of these. Remove the suppressions in
order to show any remaining issues on the waterfall.

BUG=694359,715696
NOTRY=true
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2852623003
Cr-Commit-Position: refs/heads/master@{#468190}

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

@@ -705,8 +705,6 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
         ['linux'], bug=483282)
     self.Fail('conformance2/textures/image_bitmap_from_image/' +
               'tex-3d-r16f-red-float.html', ['linux'], bug=679695)
-    self.Fail('conformance2/textures/canvas_sub_rectangle/' +
-              'tex-2d-rgb16f-rgb-float.html', ['linux'], bug=715696)
 
     # Linux Multi-vendor failures.
     self.Skip('deqp/data/gles3/shaders/qualification_order.html',
@@ -730,15 +728,6 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
         ['linux', 'nvidia'], bug=672380)
     self.Fail('conformance2/glsl3/vector-dynamic-indexing-swizzled-lvalue.html',
         ['linux', 'nvidia'], bug=709351)
-    self.Fail('conformance2/textures/canvas_sub_rectangle/' +
-        'tex-2d-r11f_g11f_b10f-rgb-half_float.html',
-        ['linux', 'nvidia'], bug=694359)
-    self.Fail('conformance2/textures/canvas_sub_rectangle/' +
-        'tex-2d-rgb16f-rgb-half_float.html',
-        ['linux', 'nvidia'], bug=694359)
-    self.Flaky('conformance2/textures/canvas_sub_rectangle/' +
-        'tex-2d-rgb565-rgb-unsigned_byte.html',
-        ['linux', 'nvidia'], bug=694359)
     self.Fail('conformance2/textures/image_bitmap_from_canvas/' +
         'tex-3d-srgb8_alpha8-rgba-unsigned_byte.html',
         ['linux', 'nvidia'], bug=679677)