Bug 1360508: Adjust text-combine properly. r=jryans

Text style is always resolved via ServoStyleSet::ResolveStyleForText, either
from the frame constructor initially, or from
ServoRestyleManager::ProcessPostTraversalForText.

So text-only adjustments should go there instead. Since that doesn't call into
cascade(), all the code that passes `pseudo` there is dead code we can remove.

MozReview-Commit-ID: jpbBYpLlUL
Signed-off-by: Emilio Cobos Álvarez <emilio@crisal.io>

layout/style/ServoBindingList.h

@@ -338,7 +338,8 @@ SERVO_BINDING_FUNC(Servo_ComputedValues_GetForAnonymousBox,
                    RawServoStyleSetBorrowed set)
 SERVO_BINDING_FUNC(Servo_ComputedValues_Inherit, ServoComputedValuesStrong,
                    RawServoStyleSetBorrowed set,
-                   ServoComputedValuesBorrowedOrNull parent_style)
+                   ServoComputedValuesBorrowedOrNull parent_style,
+                   mozilla::InheritTarget target)
 
 // Initialize Servo components. Should be called exactly once at startup.
 SERVO_BINDING_FUNC(Servo_Initialize, void,

layout/style/ServoStyleSet.cpp

@@ -366,7 +366,9 @@ ServoStyleSet::ResolveStyleForText(nsIContent* aTextNode,
   const ServoComputedValues* parentComputedValues =
     aParentContext->StyleSource().AsServoComputedValues();
   RefPtr<ServoComputedValues> computedValues =
-    Servo_ComputedValues_Inherit(mRawSet.get(), parentComputedValues).Consume();
+    Servo_ComputedValues_Inherit(mRawSet.get(),
+                                 parentComputedValues,
+                                 InheritTarget::Text).Consume();
 
   return GetContext(computedValues.forget(), aParentContext,
                     nsCSSAnonBoxes::mozText,
@@ -377,9 +379,13 @@ ServoStyleSet::ResolveStyleForText(nsIContent* aTextNode,
 already_AddRefed<nsStyleContext>
 ServoStyleSet::ResolveStyleForFirstLetterContinuation(nsStyleContext* aParentContext)
 {
-  const ServoComputedValues* parent = aParentContext->StyleSource().AsServoComputedValues();
+  const ServoComputedValues* parent =
+    aParentContext->StyleSource().AsServoComputedValues();
   RefPtr<ServoComputedValues> computedValues =
-    Servo_ComputedValues_Inherit(mRawSet.get(), parent).Consume();
+    Servo_ComputedValues_Inherit(mRawSet.get(),
+                                 parent,
+                                 InheritTarget::FirstLetterContinuation)
+                                 .Consume();
   MOZ_ASSERT(computedValues);
 
   return GetContext(computedValues.forget(), aParentContext,
@@ -399,7 +405,10 @@ ServoStyleSet::ResolveStyleForPlaceholder()
   }
 
   RefPtr<ServoComputedValues> computedValues =
-    Servo_ComputedValues_Inherit(mRawSet.get(), nullptr).Consume();
+    Servo_ComputedValues_Inherit(mRawSet.get(),
+                                 nullptr,
+                                 InheritTarget::PlaceholderFrame)
+                                 .Consume();
   MOZ_ASSERT(computedValues);
 
   RefPtr<nsStyleContext> retval =

layout/style/ServoTypes.h

@@ -71,6 +71,8 @@ enum class UpdateAnimationsTasks : uint8_t {
   CascadeResults   = 1 << 3,
 };
 
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(UpdateAnimationsTasks)
+
 // The mode to use when parsing lengths.
 enum class LengthParsingMode {
   // In CSS, lengths must have units, except for zero values, where the unit can
@@ -83,7 +85,16 @@ enum class LengthParsingMode {
   SVG,
 };
 
-MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(UpdateAnimationsTasks)
+// The kind of style we're generating when requesting Servo to give us an
+// inherited style.
+enum class InheritTarget {
+  // We're requesting a text style.
+  Text,
+  // We're requesting a first-letter continuation frame style.
+  FirstLetterContinuation,
+  // We're requesting a style for a placeholder frame.
+  PlaceholderFrame,
+};
 
 } // namespace mozilla