Add more precise DCHECKs to float feature info

gpu/command_buffer/service/feature_info.cc

Index: gpu/command_buffer/service/feature_info.cc
diff --git a/gpu/command_buffer/service/feature_info.cc b/gpu/command_buffer/service/feature_info.cc
index 14be4fd1628f63a875ec6bf458fbeed63d6f0531..c2eaf0188ec38e43c79ecd80f9441dd9d867f309 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -1378,6 +1378,9 @@ void FeatureInfo::InitializeFeatures() {
 
 void FeatureInfo::InitializeFloatAndHalfFloatFeatures(
     const StringSet& extensions) {
+  // No errors should be present before running this function.
+  DCHECK_EQ(glGetError(), static_cast<GLuint>(GL_NO_ERROR));
+
   // Check if we should allow GL_OES_texture_float, GL_OES_texture_half_float,
   // GL_OES_texture_float_linear, GL_OES_texture_half_float_linear
   bool enable_texture_float = false;
@@ -1503,6 +1506,9 @@ void FeatureInfo::InitializeFloatAndHalfFloatFeatures(
                      formats[i], GL_FLOAT, NULL);
         full_float_support &= glCheckFramebufferStatusEXT(GL_FRAMEBUFFER) ==
                               GL_FRAMEBUFFER_COMPLETE;
+        DCHECK_EQ(glGetError(), static_cast<GLuint>(GL_NO_ERROR))
+            << " with internal format " << internal_formats[i] << " and format "
+            << formats[i] << ".";
       }
       enable_ext_color_buffer_float = full_float_support;
     }
@@ -1527,6 +1533,9 @@ void FeatureInfo::InitializeFloatAndHalfFloatFeatures(
         full_half_float_support &=
             glCheckFramebufferStatusEXT(GL_FRAMEBUFFER) ==
             GL_FRAMEBUFFER_COMPLETE;
+        DCHECK_EQ(glGetError(), static_cast<GLuint>(GL_NO_ERROR))
+            << " with internal format " << internal_formats[i] << " and format "
+            << formats[i] << ".";
       }
       enable_ext_color_buffer_half_float = full_half_float_support;
     }