Advertise EXT_float_blend in ES 3.2

By comparing OpenGL ES 3.0, 3.1, and 3.2 spec side by side, we could safely assert that floating-point is core in and only in GL ES 3.2.
Thus we should advertise EXT_float_blend enable float 32 blending on GL ES 3.2 backend regardless of whether it is listed.

* ES 3.0, section 4.1.7: Blending applies only if the color buffer has a fixed-point format. If the color buffer has an integer format, proceed to the next operation.
* ES 3.1, section 15.1.5: Blending applies only if the color buffer has a fixed-point ~~or floating-point~~ (it’s striked through in the original source), format. If the color buffer has an integer format, proceed to the next operation.
* ES 3.2, section 15.1.5: Blending applies only if the color buffer has a fixed-point or floating-point format. If the color buffer has an integer format, proceed to the next operation


Bug: 964208, 970532
Change-Id: I7b7ec375f6b0ac34276d6cfec92c4956d7c1f6cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1649055
Commit-Queue: Shrek Shao <shrekshao@google.com>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#667218}

gpu/command_buffer/service/feature_info.cc

@@ -1680,8 +1680,9 @@ void FeatureInfo::InitializeFloatAndHalfFloatFeatures(
     }
   }
 
-  // Assume all desktop (!gl_version_info_->is_es) supports float blend
-  if (!gl_version_info_->is_es ||
+  // Assume all desktop (!gl_version_info_->is_es) supports float blend.
+  // Floating-point format blending is core of ES 3.2.
+  if (!gl_version_info_->is_es || gl_version_info_->IsAtLeastGLES(3, 2) ||
       gfx::HasExtension(extensions, "GL_EXT_float_blend")) {
     if (!disallowed_features_.ext_float_blend) {
       EnableEXTFloatBlend();